细胞外基质中金属蛋白酶的结构和功能
基质金属蛋白酶
生命科学研究LIFE SCIENCE RESEARCH1999年 第3卷 第3期 Vol.3 No.3 1999基质金属蛋白酶吴二喜 王凤飞 Norman McKIE摘 要：基质金属蛋白酶是一类分解细胞外基质组分的锌蛋白酶。
它们在有机体生长发育中的细胞外基质逆转与重塑以及疾病中的病理损害起着极为重要的作用。
基质金属蛋白酶的表达和活性在不同细胞水平受到严密调控，如细胞因子、生长因子以及激素的调节。
基质金属蛋白酶以酶原形式分泌，随后被其它蛋白酶如胞浆素或非蛋白酶类化学物质如有机汞所激活。
所有基质金属蛋白酶都受到天然抑制剂金属蛋白酶组织抑制剂所抑制。
两者的不平衡导致许多疾病的发生，如肿瘤侵入及转移。
合成基质金属蛋白酶组织抑制剂所抑制，如Marimastat能控制肿瘤转移的发生及进一步扩散。
本文将对基质金属蛋白酶的特征、分子区域结构、底物特性、激活机制、调控方式等方面进行最新概述。
关键词：基质金属蛋白酶；金属蛋白酶组织抑制剂；胶原酶；明胶酶；基质酶；膜型基质金属蛋白酶中图分类号：Q51；Q55 文献标识码：AMatrix MetalloproteinasesWU Er-xi1*，WANG Feng-fei1*，Norman McKIE2（1．Department of Human Metabolism and Clinical Biochemistry，University of Sheffield Medical School，Beech Hill Road，Sheffield S10 2RX，UK； 2．Department of Rheumatology，University of Newcastle-upon-Tyne Medical School Framlington Place，Newcastle-upon-Tyne NE2 4HH，UK）Abstract：Matrix metalloproteinases (MMPs) are zinc proteinases that degrade compounds of the extracellular matrix (ECM). These enzymes play a pivotal role in turnover and remodelling of the ECM during organism growth and development and the pathological destruction of tissues in diseases. The activities of metalloproteinases are tightly controlled at several different cellular levels such as modulation by cytokines, growth factors and hormones. MMPs are secreted as zymogens which can be activated by other proteinases such as plasmin or non-proteolytic agents such as organomercurials. All MMPs are inhibited by their natural inhibitors,tissue inhibitors of matrix metalloproteinases(TIMPs). Imbalance between MMPs and TIMPs has been implicated in many diseases such as tumour invasion and metastasis. The synthetic MMP inhibitors such as Marimastat can prevent the growthand further spread of established metastases.Key words：MMPs；TIMPs；collagenases；gelatinases；stromelysins；membrane type MMPsT0 Introduction Matrix metalloproteinases (MMPs) are also called matrixins. Since the first MMP was discovered by Gross and Lapiere in 1962, numerous other MMPs have been described and characterized. To date at least 14 MMPs have been found (Table 1). According to their structural properties and substrate specificities, MMPs can be divided into sub-Table 1 The matrix metalloproteinase family*Enzymes MMP No．**EC No．Mr（kDa）latent/activeExtracellular matrixsubstratesCollagenases Interstitial collagenase MMP1EC 3．4．24．757/48Collagen Ⅰ，Ⅱ，Ⅲ，Ⅶ，Ⅹ；gelatin，entactin，tenascin，aggrecan，progelatinaseA，progelatinase BNeutrophil collagenase MMP8EC3．4．24．3485/65Collagen Ⅰ，Ⅱ，Ⅲ；aggrecanCollagenase 3MMP13 60/48Collagen Ⅰ，ⅡGelatinases Gelatinase A MMP2EC 3．4．24．2472/66Collagen Ⅰ，Ⅳ，Ⅴ，Ⅶ，Ⅹ；gelatin，fibronectin，laminin，aggrecan elastin，progelatinase BGelatinase B MMP9EC 3．4．24．3592/84Collagen Ⅳ，Ⅴ；gelatin，elastin，entactin，aggrecan，vitronectinStromelysins Stromelysin 1MMP3EC 3．4．24．1760/50Collagen Ⅱ，Ⅳ，Ⅸ，Ⅹ，Ⅺ；gelatin，laminin，fibronectin，elastin，tenascin，aggrecan，procollagenase，progelatinase B，neutrophil procollagenaseStromelysin 2MMP10EC 3．4．24．2253/47Collagen Ⅳ，laminin，fibronectin，elastin，aggrecan，procollagenaseStromelysin 3MMP11 65/45Serpins，α1-PI，α2-antiplasmin，insulin-like growth factor-bindingprotein-1Others Matrilysin MMP7EC 3．4．24．2328/21Collagen Ⅳ，gelatins，laminin，fibronectin，entactin，elastin，aggrecan，progelatinaseA，progelatinase B，procollagenaseMetalloelastase MMP12EC．3．4．24．6552/43ElastinMembrane type MMPs MT1-MMP MMP14 63/54Progelatinase A，procollagenase 3，collagen，proteoglycan，fibronectin，tenascinMT2-MMP MMP15 72/61Progelatinase A，procollagenase 3，collagen，proteoglycan，fibronectin，tenascinMT3-MMP MMP16 64/55Progelatinase A MT4-MMP MMP17 70/54Unknown*Compiled from sources including Sang and Douglas[2]；Shingleton et al．[3]；Nagase [4]；Pei et al．[19]；Mari et al．[44]；Murphy et al．[96]；Takino et al．[28，46]andCockett et al．[116]**Some MMPs have been omitted．MMP5 and MMP2 are the same enzyme[5]，MMP4 and MMP6 have been described in only one laboratory and there are no sequence data to date [5]．There are some novel MMPs which have been found recently，see text for details．groups: collagenases, gelatinases, stromelysins, membrane type MMPs (MT-MMP) andothers[1～4]. This review summarises the characteristics, domain structure, substratespecificity, activation mechanisms, regulation, functions of the MMPs.1 Main characteristics of the MMPs All MMPs have a number of common characteristics which are also helpful to identify new members. These properties[2, 5～7]are: 1）they share a common domain structure comprising signal, propeptide, catalytic, and C- terminal hemopexin-like domains (except MMP7) (Fig．1).Fig．1 The domain structure of the matrix metalloproteinases2）They are secreted as zymogens. 3）Their activation can be achieved by other proteinases or organomercurials. 4）Their proteinase activity is blocked by 1,10-phenanthroline and chelating agents. 5）Activation is accompanied by a loss of molecular weight. 6）The active site contains metal ion zinc. 7）Their activity is inhibited by tissue inhibitor of metalloproteinases (TIMPs). 8）The active enzymes cleave one or more components of the extracellular matrix. 9）The enzymes act in neutral pH and need calcium ions for stability.2 Domain structure of MMPs After comparing the primary amino acid sequences of the MMP members, it can be seen that these proteins are divided into several distinct domains that are conserved among family members[1]. The largest MMP member (MMP9) has 7 domains in order from N-terminal: signal, propeptide, catalytic, fibronectin-like,α2V collagen-like, hinge, and C-terminal hemopexin-like. The simplest member MMP7 has only signal, propeptide and catalytic domains. The newly discovered MT-MMPs have a transmembrane domain[8]. All MMPs produce a signal as a leader sequence which cells cleave prior to secretion. The propeptide is lost on activation. For example, the human fibroblast collagenase is synthesized as a preproenzyme of Mr 54 kDa (57 kDa in Table 1) with the signal peptide of19 amino acids[9]. The primary secretion products of human fibroblast collagenase consist ofa minor glycosylated form of Mr 57 kDa and a major unglycosylated polypeptide of Mr 52 kDa[9]. 81 amino acids are removed after proteolytic activation of human fibroblast collagenase[9]. The catalytic domain contains a conserved zinc binding site comprising the sequence HEXGHXXGXXH[2]. The zinc acts as an active site and is ligated by the three-histidine residues of the zinc binding consensus sequence. The glutamic acid residue in the conserved zinc binding site acts as the catalytic base and proton shuttle during proteolysis and is involved in the fixation of a zinc-bound water molecule[10]. The structural integrity of the zinc-binding active site is maintained by a conserved methionine that is called “Met-turn”[10]. The catalytic domain also contains a calcium-binding region where the calcium ion is believed to stabilize the enzyme[11]. With the exception of matrilysin (MMP7), the MMPs contain an additional feature, that is their hemopexin-like or vitronectin-like C-terminal domain[1]. This domain is thought to help determine substrate specificity[1,5]. Thiscould be true, since recently Gohlke et al.[12]have found that the topology and the side chain arrangements of gelatinase A (MMP2) and fibroblast collagenases are very similar, but there are significant differences in surface charge and contouring. They thought these differences may be a factor in allowing the MMP2 C-terminal domain to bind to TIMP2. Very recently, Brooks et al.[13,14]have found that MMP2 can bind αvβ3 through its hemopexin-like domain. Besides the prototype domain structure, the gelatinases contain three tandem domains with sequences similar to the collagen-binding domain of fibronectin. The fibronectin-like domain is thought to be involved in the binding of two gelatinases to their substrate[5]. The MT-MMPs contain a transmembrane domain and a furin recognition site which is also found in stromelysin 3[8,15](Fig．1).3 Substrate specificity of MMPs The collagenases mainly cleave interstitial collagens (type I, II and III), unlike other MMPs, their substrate specificity is well defined. Collagenase action on the α2-macroglobulin results in the cleavage of Gly-Leu Peptide bond[5]．They cleave the Gly-Ile peptide bond of α1(I) chain of collagen and Gly-Leu peptide bond of α2(I) chain of collagen[5]. The substrate cleavage pattern for collagenases is that P1 "residue is invariably hydrophobic (Leu, Ile, Val) and that P1 is usually Gly or a hydrophobic residue[5,16]. The gelatinases cleave denatured collagens and type IV collagen. As shown in table 1, while gelatinase A (MMP2) can also cleave the fibronectin and laminin, major components of the basement membrane, gelatinase B (MMP9) can only cleave the basement membrane component entactin[2]. Stromelysin 1 and 2 have a broad pH optimum and more general activity and are able to degrade many ECM proteins including proteoglycans, gelatins, fibronectin, laminin, elastin, type IV collagen and type IX collagen[17]． Niedzwiecki et al.[18]tested the substrate specificity of the human stromelysin 1 and found the preferences at P3, P2, P1, P1 ", and P2 "are for the hydrophobic amino acids Pro, Leu, Ala, Nva, and Trp, respectively. The mature stromelysin 3 does not degrade any major ECM components. Up to now, the only known substrates for stromelysin 3 are α1-proteinase inhibitor, serine proteinase inhibitors, α2-antiplasmin, and insulin-like growth factor-binding protein-1 [19,20]. However, the substrate specificity overlaps among the MMP members. The gelatinase A (MMP2) can also cleave triple helical type I collagen generating the 3/4 and 1/4 length collagen fragments characteristic of interstitial collagenases[21]. The cleavage site is the same Gly-Ile/Leu bond as the interstitial collagenases[21]. In fact all of the MMPs cleave gelatin and fibronectin at some rate[1]. Almost every MMP degrades an octapeptide containing collagen sequence GPQGIAGQ[5].4 Activation mechanisms of MMPs The MMPs are secreted in a latent form that is subsequently converted into the mature enzymes. The inactive zymogen can be processed into active forms by numerous reagentsincluding proteinases such as trypsin and plasmin; conformational perturbants such as sodium dodecyl sulfate (SDS); heavy metals such as Au (I) compounds and organomercurials; oxidants such as NaSCN; disulfide reagents such as oxidized glutathione; and sulfhydryl alkylating agents such as N-ethylmaleimide[22]. The latent proform of MMPs contains the highly conserved PRCGVNPD sequence with an unpaired cysteine residue. The cysteine residue links to the active site zinc, which blocks the active site. A ‘cysteine switch’ activation mechanism has been proposed[22,23](Fig． 2). In other words, in the latent form of MMPs, the cysteine residue with the thiol group coordinates the catalytically essential zinc ion in the active site of enzyme. Some reagents such as SDS can dissociate the cysteine residue from the zinc ion[22]. From this hypothesis, each MMP should have an unpaired cysteine residue and a zinc-binding site. In fact, all MMPs contain the PRCGVNPD sequence with an unpaired cysteine residue in the propeptide domain and the HEXXHXXGXXH sequence in the catalytic domain. Very recently, it has been shown that he structure of human pro-MMP2 supports this hypothesis[24]. The loops within the propeptide domain act as bait for activating proteinases. The prodomain structure breaks down and its shielding of the catalytic cleft is withdrawn upon cleavage, which allow water to enter and hydrolyze the coordination of the cysteine residue to the zinc ion[24]. All MT-MMPs found to date and stromelysin 3 contain a consensus sequence RXR/KR, which has already been found to be essential in the activation of stromelysin 3 and MT1-MMP by furin [15,25,26]. MMPs also have the ability to activate one another[27]. MT1-MMP[8]and MT3-MMP[28]have been shown to activate MMP2. MMP7 can activate MMP1, MMP2, MMP3 and MMP9[29]. MMP3 activates MMP1[30], MMP8[31], MMP9[32]and MMP13[33]. MMP2 and MT1-MMP activate MMP13[34], while MMP10 activates MMP8[35]. It has also been well documented that MMPs and serine proteinases can act on the proforms of one another [36,37]. Plasmin can cleave the prodomains of MMPs such as collagenase and stromelysin and activate these enzymes[36,37]. MMP7 can catalyze the formation of low molecular weight pro-urokinase and urokinase[38].Fig．2 Cysteine switch mechanism for activation of MMPsProteinases such as trypsin and plasmin cleave the propeptide，ahead of the cysteine to generate intermediate forms．Alternatively，nonproteolytic agents such as aminiphenyl-mercuric acetate （APMA） and sodium dodecy1 sulfate （SDS） will modify the cysteine．In a second step，these intermediate forms can be autoproteolytically cleaved to remove the propeptide and confer permanent activity．5 Regulation of MMPs The activities of metalloproteinases are tightly controlled at several different cellular levels. There are five points: (i) modulation of gene expression by cytokines, growth factors and hormones; (ii) synthesis and secretion of proMMPs; (iii) selective expression of MMP genes in specific tissue/cell types; (iv) activation of proenzymes; and (v) inhibition of the active enzymes[7,36,39,40]. It is known that the MMPs are not constitutively expressed in most tissue types but their mRNAs can be induced by treatment with many kinds of agents such as cytokines, growth factors, hormones, tumour promoter and oncogene products. In some cases the induction of more than one MMP is coordinately regulated, for example, MMP1 and MMP3 are often coordinately expressed[40]. The synthesis of MMP1 and MMP3 can be upregulated by 12-O-tetradecanoyl-phorbol-13-acetate (TPA), interleukin 1 (IL1), tumor necrosis factor α(TNFα), epidermal growth factor (EGF), basic fibroblast growth factor (bFGF) and platelet derived growth factor (PDGF) and be downregulated by transforming growth factor β (TGF-β), interferon γ (IFN-γ) retinoic acid and dexamethasone[40], and MMP1 is down regulated by IL4[41]. The selective expression of MMP genes in specific tissue/cell types is one method of regulation of MMPs. Interstitial collagenase (MMP1) arises from connective tissue fibroblasts and macrophages. Neutrophil collagenase (MMP8) is only produced by cells of the neutrophil lineage. Stromelysin 1 (MMP3) is not widely expressed normally, but can be readily induced by growth factors, cytokines, tumour promoters and oncogene products in cultured mesenchymal cells such as chondrocytes and connective tissue fibroblasts. Stromelysin 2 (MMP10) is usually expressed in macrophages, keratinocytes and tumour cells[40,42]. Stromelysin 3 (MMP11) is often expressed in tumour stromal cells[37,40,43,44]. Gelatinase A (MMP2) is the most widespead of all MMPs and is frequently elevated in malignancies as well as occurring in connective tissue cells[36,40]. Gelatinase B (MMP9) is expressed in transformed and tumour-derived cells, neutrophil, corneal epithelial cells, cytotrophoblasts and keratinocytes[36]. Matrilysin is expressed in immature monocytes[36]. Metalloelastase (MMP12) is found in macrophages. MT1-MMP is expressed in tumour stroma cells[45]. MT2-MMP is produced by a human oral malignant melanoma and a human placenta[46]. MT3-MMP is expressed in normal tissues such as lung and kidney and cultured cells such as the squamous cell carcinoma cell line OSC-19 and human embryonal lung fibroblasts[28]. MT4-MMP is expressed in primary breast carcinomas and breast cancer cell lines examined[47]. All MMPs are inhibited by natural inhibitors called tissue inhibitors of metalloproteinases (TIMPs) of which four have been described (Table 2). TIMPs 1, 2 and 4 are secreted extracellularly in soluble form whereas TIMP3 binds to the ECM. All TIMPs share 35%～40% sequence identity and considerable higher structural similarity. The TIMPs bind with high affinity and 1∶1 molar ratio to active MMPs resulting in the loss of proteinase activity. All TIMPs contain 12 cysteine residues that have been shown to form disulfide bonds generating 6 loops. The mechanism of inhibition of MMPs by TIMPs is widely felt to be unclear. Murphy[39]. pointed out that the TIMP C-terminal domain has several different MMP binding sites that act to increase the rate of inhibition. Further studies such as site-directed mutagenesis and the crystal structure research of the complex of MMP and TIMP will facilitate understanding of the mechanism. TIMPs play a pivotal role in the regulation of ECM degradation/remodelling. Disruption of the balance between MMPs and TIMPs has been implicated in many diseases such as tumour invasion and metastasis. Besides their inhibitory activities, the TIMPs play a role in growth-promotion[48]. Some effective synthetic MMP inhibitors also can inhibit MMPs[49,50]. For example, the hydroxamate-based inhibitors such as BB94 (batimastat) and BB2516 (marimastat) can inhibit metastatic spread of tumoursand block the process of tumour neovasculariation[51～54]. The hydroxamate group in thesemolecules can combine with the zinc atom in the active site of MMPs[49,50].Table 2 Comparison of TIMP family members* TIMP1TIMP2TIMP3TIMP4 Molecular mass28kDa21kDa24kDa22kDa Glycosylation yes no no/yes no Binding properties proMMP9proMMP2ECM proMMP2Transcripts0.9kb 1.1 and 3.5kb 4.5,2.8,2.4and 1.2kb1.4，4.1，2.1，1.2，and 0.97kbModulation of gene expression by TGF-β1updown or noobvious effectup not determinedMajor sites ofexpressionOvary，bone Placenta Kidney，brain Heart Chromosome locationof human genexq1117q2522q12.1～13.22p25 *Compiled from sources including Stetler-Stevenson[117]；Greene et al．[118]；Wick et al．[119]；Chamber and Matrisian[120]and Olson et al．[121]6 MMPs in physiological processes and pathological destruction Normal expression of MMPs is associated with turnover and remodelling of the ECM during growth and development. Cawston[7]summarised the involvement of MMPs in the normal turnover of connective tissue matrix. The MMPs are involved in the normal physiological processes such as ovulation and embryo implantation, embryological development, angiogenesis, bone turnover, uterine resorption and cervical ripening[7]. The MMPs are associated with the pathological destruction of tissues in diseases[1,7]. They are implicated in the processes such as wound healing, corneal ulceration, tumour growth and metastasis, periodontal disease, rheumatoid arthritis, arteriosclerosis and aortic aneurism[1,7]. Considerable research has been directed toward understanding both the steps involved in tumour cell invasion and metastasis and the molecular mechanism of the process. MMPs are thought to be one of the main contributors to tumour invasion and metastasis since they can degrade all of the components of basement membranes which the tumour cellsmust traverse[55～58]. Now the gene-targeting experiments have facilitated the examinationsof the effects that their absence, mutation or overexpression, in various physiological and pathological processes[59]. In the following sections more detailed information is presented on several MMP family members.7 Collagenases I, II and III (MMP1, MMP8 and MMP13) The group of enzymes termed collagenases includes 3 members: MMP1 (interstitialcollagenase or fibroblast collagenase), MMP8 (neutrophil collagenase) and MMP13 (collagenase 3). Their sequences share around 50%[33]. They cleave all three α chains of native types I, II, III collagens at a single site resulting in fragments corresponding to three-quarters and one-quarter of their initial length by hydrolyzing the peptide bond Gly-[Ile orLeu][60～62]. They do not degrade collagen IV and V, which are cleaved by otherproteinases[63～66]. The collagenases can also cleave type X collagen[67]. The threecollagenases have their own preference in cleaving the collagens. The preferred substrate of collagenase 3 (MMP13) is collagen type II[33], fibroblast collagenase (MMP1) preferentially cleaves collagen type III[68]and neutrophil collagenase (MMP8) prefers to cleave type I collagen[69]. Also collagenase 3 has a much stronger gelatinolytic activity than its homologous counterparts MMP1 and MMP8[33]. To date MMP1 expression has not been found in rats or mice[33]. All collagenases are located in the human chromosome 11q22.3 cluster[70,71]and share a highly conserved gene structure[72,73]. The expression of MMP13 in cartilage and its preference to degrade type II collagen suggests that it plays a critical role in the arthritides[74]. X ray crystallographic analyses of MMP1 and MMP8 are available now. The structures show that their catalytic domains harbour two zinc ions and one or twocalcium ions[75～77]. The structure consists of a five-stranded β sheet and three α helices[75].8 Gelatinases A and B (MMP2 and MMP9) Gelatinases, also called type IV collagenases, contain two members: MMP2 and MMP9. They degrade denatured collagens, type IV, V, VII, X, and XII collagens,vitronectin, aggrecan, elastin, galectin 3 and laminin[78～83]. Recently, it has beendemonstrated that MMP2 degrades native interstitial collagens[21]. MMP2 is the most widely distributed MMP[1]. Overexpression of gelatinases has been demonstrated in many tumorsystems and has been linked to tumour invasion[84～87]. While the proMMP2 is often foundcomplexed with the TIMP2 and is activated by MT1-MMP[88,89], the proMMP9 is associated with the TIMP1[78,90]. The regulation of MMP2 and MMP9 gene expression is different[91]. The promoter of MMP9 gene has a TATA-like sequence and a TPA response element, while MMP2 gene has no TATA motif-like sequence in the vicinity of the start site for transcription and TPA response element in its promoter[91]. There is a structural difference between MMP2 and MMP9 that comprises an extended 54 amino acid hinge region sequence which shares some homology with the α2 chain of type V collagen[78]. Brooks et al.[13,14]have found that MMP2 can directly bind integrin αvβ3. They further demonstrated that MMP2 binds αvβ3 through its hemopexin-like domain. It is likely to be distinct from other αvβ3-directed ligands as MMP2 has no RGD sequence[13,14]. Brooks et al.[14]have also found that PEX, a fragment of MMP2, which contains the C-terminal hemopexin-like domain, prevents MMP2 binding to αvβ3 and blocks cells surfacecollagenolytic activity. PEX is likely to be a natural breakdown product of MMP2 since the active form (62 kDa) of MMP2 can be further processed to a smaller species (43 kDa) resulting from autocatalytic removal of the 29 kDa hemopexin-like domain without the presence of TIMP2[14,92]. Both MMP2 and MMP9 are located on human chromosome 16[93].9 Stromelysins 1, 2 and 3 (MMP3, MMP10 and MMP11) MMP3 (stromelysin 1), MMP10 (stromelysin 2) and MMP11 (stromelysin 3) belong to this group. Stromelysins have wide substrate specificity. Stromelysin 1 degrades aggrecan, fibronectin， gelatin， laminin， type II， IV， IX， X， XI collagens and elastin[2,94]. It also participates in activation of other proMMPs such as proMMP1, proMMP8 and proMMP9[31,32,80]. MMP3 is not readily expressed in tissue but can be induced by cytokines such as IL1 and TNFα, growth factors and tumour promoters such as PMA[1,5,95]. Stromelysin 2 cleaves aggrecan, laminin, fibronectin, elastin and type IV[2]. It is transcriptionally active in normal human cells such as keratinocytes and it encodes the secreted Stromelysin 2[42]. Stromelysin 3 is a newly characterized MMP. It can degrade serpin, α1-proteinase inhibitor (α1-PI), α2-antiplasmin, and insulin-like growth factor-binding protein-1[19,20]; the truncated stromelysin 3 can also degrade fibronectin, laminin, aggrecan and type IV[96]. Stromelysin 3 is often found expressed in stromal cells surrounding primary and metastatic carcinomas[43]and may be involved in promoting local tumor development. Recently it has been suggested that the tumor-specific processing of stromelysin 3 to the 35 kDa protein is likely to be an important regulatory mechanism, since the generation of 35 kDa stromelysin in tumour/stroma coculture requires basic fibroblast growth factor (bFGF) and an MMP-like enzyme[44]. Unlike other MMPs, prodomain of stromelysin 3 contains a furin cleavage site, and therefore stromelysin 3 can be processed directly to its 45 kDa active form by furin within the constitutive secretory pathway[15]. MMP3 and MMP10 are located in the human chromosome cluster 11q22.3[70,72], while MMP11 is mapped to the Q11.2 region of chromosome 22[97]．10 Membrane type-matrix metalloproteinases (MMP15, MMP16, MMP17 and MMP18) Membrane type matrix metalloproteinases (MT-MMPs), comprising MT1-MMP, MT2-MMP2, MT3-MMP and MT4-MMP (MMP14, MMP15, MMP16 and MMP17, respectively) are a novel subgroup of MMPs which contain a transmembrane domain and a short cytoplasmic domain in addition to the signal, pro-, catalytic, hemopexin-like and C-terminal domains which are common to other MMPs. To date, four MT-MMPs have been described [8,28,47,98]. From the alignment of amino acid sequences for MT-MMPs[47], it can be seen that they have at least 30% sequence homology to each other. Like other MMPs, they contain cysteine switch sequence, zinc binding site and Met-turn. However, they have an insertion between the propeptide and the catalytic domain in addition to the above mentionedmembrane-binding domain and short cytoplasmic domain. This insertion as in stromelysin 3 contains a potential cleavage site of furin or furin like convertase[8,15]. It has already been demonstrated that furin can cleave this sequence in pro-stromelysin 3 and proMT1-MMP [15,25,26]. However, the proMT1-MMP is proteolytically activated by human plasmin[99]. Okumura et al.[99]proposed that this is an extracellular proteinase activator of proMT1-MMP whereas the intracellular mechanism of activation is mediated by furin or a furin-like enzyme. The second insertion is found in proteinase domain; the function of these 8 amino acids is not known. The third insertion which contains the hydrophobic transmembrane domain is located in the C-terminal. The transmembrane domain of MT-MMPs plays an essential role in the progelatinase A (proMMP2) activation function of MT-MMPs, although some portions of the truncated form remain on the cell surface after the removal of this domain[100]. In MT1-MMP, the activation complex is a trimer comprising MT1-MMP, progelatinase A and TIMP2[88,89]. A recent study has suggested that MT1-MMP is a TIMP2 receptor[101]. This is further confirmed by another recent study[73]that TIMP2 and MT1-MMP form a complex for activation of progelatinase A. TIMP2 and TIMP3 can efficiently inhibit MT1-MMP whereas TIMP1 is a poor inhibitor for MT1-MMP[102]. Will et al.[102] also demonstrated that TIMP2 and TIMP3 can bind more rapidly to the catalytic domain of MT1-MMP than to the catalytic domain of MMP2. At the same time, two groups showed that MMP14, MMP15 and MMP16 locate in chromosomes 14, 16 and 8, respectively [103,104]. The MT-MMP gene loci are dispersed whereas most MMPs are clustered on chromosome 11q22.3[70,71], suggesting that the MT-MMPs may be a genetically distinct subgroup of MMPs. It has been suggested that the MT-MMPs play a critical role in tumor cell invasion and in ECM degradation[8,57,102]. MT-MMPs also can degrade ECM components[25,105,106].11 Others This group includes MMPs such as matrilysin (MMP7) and metalloelastase (MMP12). Matrilysin, also called putative metalloproteinase 1 (pump 1), is the smallest member of the MMP family. Unlike other MMPs, it lacks a C-terminal hemopexin-like domain. MMP7 can degrade various ECM components. It also can activate other proMMPs such as proMMP1, 3, 2 and 9[29]. Metalloelastase (MMP12) is also called macrophage elastase (ME). The expression of human macrophage elastase (HME) is mainly restricted to tissue macrophages [107]. Besides the substrate elastin listed in Table 1, the purified recombinant HME can degrade fibronectin, laminin, entactin, type IV collagen, chondroinan sulfate, and heparan sulfate[108]. Chandler et al.[109]also demonstrated that HME can degrade myelin basic protein and processes a TNF α fusion protein. Therefore Gronski et al.[108]suggested that HME may be essential for macrophages to penetrate basement membranes and remodel injured tissue during inflammation. MMP7 and MMP12 are allocated in the human chromosome cluster 11q22.3[70,72,107].。
tace 化学结构-概述说明以及解释
tace 化学结构-概述说明以及解释1.引言1.1 概述TACE（Tumor Necrosis Factor-Alpha Converting Enzyme）是一种重要的酶类蛋白，在生物学研究领域中具有广泛的应用和研究价值。
作为一种分泌型金属蛋白酶，TACE能够促进细胞表面受体的活化和底物的剪切，从而参与多种细胞信号传导途径的调控。
TACE的化学结构具有一定的复杂性和多样性。
它是一种跨膜蛋白，由于其重要的生物学功能，其结构也备受关注。
TACE包含多个结构域，包括信号肽、金属螯合结构域、膜结合结构域、Cysteine-rich 结构域和Zn组织域等。
其中，信号肽用于靶向TACE定位并促进其分泌，金属螯合结构域包含了TACE的活性位点，膜结合结构域则使其在细胞膜上得以稳定定位。
Cysteine-rich 结构域和Zn组织域则对TACE的稳定和结构完整性起到重要的作用。
在生物学中，TACE具有多样的作用。
首先，TACE通过剪切和释放细胞膜上的受体前体形式来参与信号通路的激活，如EGF受体、TNF-α等。
其次，TACE还可以调节细胞凋亡、炎症反应和免疫反应等生理过程。
此外，TACE还与许多疾病的发生和发展密切相关，如炎症性疾病、癌症和免疫相关疾病等。
因此，对TACE的化学结构及其在生物学中的作用的深入研究，对于揭示其底层机制以及疾病的防治具有重要的意义。
本文将对TACE的化学结构进行详细介绍，并探讨其在生物学中的作用。
在对TACE结构的总结之后，也将展望TACE在未来的研究方向。
通过深入了解TACE的化学结构和功能，我们可以为开发新的药物靶点和疾病治疗提供重要的依据和思路。
文章结构部分的内容如下：1.2 文章结构本文将按照以下结构展开对TACE（Tumor Necrosis Factor-αConverting Enzyme）的化学结构和生物学作用进行探讨：第一部分为引言部分，我们将对TACE的概述进行简要介绍，包括其定义、来源和重要性。
基质金属蛋白酶9
基质金属蛋白酶9
基质金属蛋白酶9（Matrix Metalloproteinase 9）又称MMP-9，是一类具有多功能的糖蛋白酶，它主要参与了许多细胞间质功能，如组织改变、生长因子和细胞因子的释放，也参与了炎症反应以及血管扩张等过程。
此外，MMP-9还可以促进细胞的浸润和迁移，并帮助血管内皮细胞形成新的血管。
MMP-9在肿瘤发生、发展中起着极其重要的作用，它可以促进血管的新生和肿瘤的侵袭，对肿瘤的发展起到关键性作用。
同时，MMP-9还可以促进肿瘤细胞的凋亡，但是目前这方面的研究尚不完整。
基质金属蛋白酶—9与心血管病的关系
基质金属蛋白酶—9与心血管病的关系基质金属蛋白酶（matrix metalloproteinases，MMPS）是由多种锌离子依赖性酶组成的、能够降解细胞外基质蛋白的重要酶类，几乎能够降解细胞基质的所有成分（胶原、明胶、粘性蛋白、纤维粘连蛋白、蛋白多糖等）。
基质金属蛋白酶-9（matrix metalloproteinase-9，MMP-9）又称明胶酶B，MMP-9不仅参与胚胎的正常发育、形态发生及月经形成等生理过程，在病理情况下，潜在型MMP-9被激活，在细胞外基质胶原重构的过程中具有重要作用，与多种心血管疾病的发生及发展有关，如心肌梗死后心室重构、充血性心力衰竭进展、心房颤动（房颤）、动脉粥样硬化斑块的形成与破裂、动脉瘤形成等。
标签：基质金属蛋白酶-9；心血管病；心肌重构在一些心血管疾病的发展过程中，除心肌细胞本身结构、代谢及功能异常外，心脏间质组织也发生异常改变。
许多实验结果表明，心肌细胞外基质（extracellular matrix，ECM）尤其是心肌胶原的异常改变，在心血管疾病的发病机制中起重要的作用。
MMPs是细胞外基质降解所必需的、锌离子依赖性的内源性蛋白酶家族，是ECM的主要生理性调节物质。
对于血管系统的基质成分而言，最重要的MMPs 是胶原酶和明胶酶，在基质成分合成与降解的过程中起着重要的作用。
现就MMP-9在心血管疾病中的影响做一综述。
1 MMP-9概述1.1 MMPs家族MMPs是自然进化中高度保守的一类酶，人们于1962年在蝌蚪尾组织中发现了第一个MMPs胶原酶，之后陆续在动植物中找到许多MMPs成员，目前已经发现MMPs近30种，在人体中已识别和定性至少23种1。
几乎全体MMPs 都有3个共同的结构域：前肽、催化结构域和血色素结合蛋白样C末端结构域。
根据其底物敏感性不同分4类：①间质胶原酶（MMP-1、8、13、18）：主要降解胶原纤维（Ⅰ、Ⅱ、Ⅲ型胶原）；②明胶酶（MMP-2、9）：主要降解变性胶原及基底膜的主要成分Ⅳ型胶原；③基质降解酶（MMP-3、7、10、11），可降解多数ECM成分：包括蛋白多糖、层粘连蛋白、纤维粘连蛋白；④膜型金属蛋白酶（MT-MMP，MMP-14、15、16、17）：能直接降解几种ECM成分和激活其他MMP；⑤未分类（MMP-19、20、23、28等）。
金属基质蛋白酶9与疾病的研究进展
金属基质蛋白酶9与疾病的研究进展摘要：金属基质蛋白酶（MMPs）是一组可以选择性降解细胞外基质（ECM）的内肽酶，金属基质蛋白酶9（MMP-9）又名明胶酶B，它是MMPs家族中一个重要成员，能水解弹性蛋白、胶原蛋白、明胶、纤维蛋白等多种细胞外基质成分，在生理情况下参与人体的正常发育，是ECM降解的生理性调节因子。
所有MMPs都受金属基质蛋白酶抑制剂所抑制，两者的不平衡导致许多疾病的发生。
金属基质蛋白酶抑制剂1（tissue inhibitor of metalloproteinase-1，TIMP-1）为MMP-9特异性抑制剂，目前认为MMP-9与TIMP-1是调节ECM降解、合成的主要酶类，MMP-9/TIMP-1比值失衡是多种疾病发生、发展的重要机制之一。
近年研究发现MMP-9还与全身多系统疾病的发生、发展有关，现就MMP-9与多种疾病的相关研究进展进行综述。
关键词：金属基质蛋白酶9；疾病；研究进展金属基质蛋白酶（matrix metalloteinases，MMPs）是一组锌离子依赖的肽链内肽酶，因含金属离子（锌、钙）而得名，现至少已发现26种MMPs，称为MMPs家族，是构成细胞外基质降解最重要的蛋白水解系统。
其抑制剂（tissue inhibitor of metalloproteinases，TIMPs）是调节MMPs的重要因素。
MMPs与TIMPs在维持ECM的动态平衡中起重要作用。
细胞外基质（extracellullar matrix，ECM）是一类由胶原、蛋白聚糖及糖蛋白等大分子物质组成的动态网状结构，ECM不仅起细胞与细胞之间机械支持和连接作用，也是细胞与细胞之间信号传递的桥梁，现已识别丝氨酸蛋白酶、半胱氨酸蛋白酶、天冬氨酸蛋白酶、基质金属蛋白酶均能降解ECM[1]。
金属基质蛋白酶9（matrix metalloteinases-9，MMP-9）是MMPs家族分子量最大的明胶酶。
基质金属蛋白酶9降解明胶
基质金属蛋白酶9降解明胶-概述说明以及解释1.引言1.1 概述基质金属蛋白酶9（MMP-9）是一种重要的酶类蛋白，广泛存在于生物体内，主要参与细胞外基质的降解和重塑过程。
明胶作为一种蛋白质，也是生物体中重要的结构分子，具有许多生理功能和应用价值。
本文将重点探讨基质金属蛋白酶9对明胶的降解作用，分析其降解机制及对生物体的影响，以期为进一步研究细胞外基质降解和生物体内蛋白质代谢提供理论基础。
部分的内容1.2 文章结构本文将首先介绍基质金属蛋白酶9的作用，包括其在生物体内的功能和重要性。
接着，将深入探讨明胶的结构与特性，介绍其在生物体中的角色和应用。
最后，将详细讨论基质金属蛋白酶9对明胶的降解机制，揭示其对生物体的影响及可能的未来研究方向。
通过这些内容的呈现，读者将对基质金属蛋白酶9降解明胶的过程有更加全面的了解，促进相关研究领域的进一步发展。
容1.3 目的目的：本文旨在探讨基质金属蛋白酶9对明胶的降解机制，以揭示其在生物体内的重要性。
通过深入了解基质金属蛋白酶9在明胶降解过程中的作用机制，可以更好地认识明胶的结构与特性，并进一步探讨明胶降解对生物体的影响。
同时，本文还将探讨未来研究方向，为相关领域的研究提供参考与借鉴。
通过本文的研究，有望为深化对基质金属蛋白酶9降解明胶的认识，从而为相关领域的科研工作提供理论支持与实验依据。
2.正文2.1 基质金属蛋白酶9的作用基质金属蛋白酶9，也称为MMP-9，是一种重要的内切酶，在细胞外基质的降解过程中起着关键作用。
它属于金属蛋白酶家族，特别善于降解胶原蛋白，是一种重要的胶原酶。
MMP-9主要通过降解胶原和基质蛋白，促进组织修复和细胞迁移。
在生理情况下，MMP-9的活性受到严格控制，只在组织修复和再生过程中被激活。
然而，在某些疾病状态下，如关节炎、癌症和心血管疾病，MMP-9的过度活化会导致病理进程的发展。
总的来说，基质金属蛋白酶9在细胞外基质降解中起着重要作用，平衡其活性对于维持正常的组织结构和功能至关重要。
肝癌的细胞外基质重塑与转移
肝癌的细胞外基质重塑与转移细胞外基质是组织的非细胞成分，由各种复杂的分子组成，包括蛋白质、糖类、脂质等。
肝癌是一种高度侵袭性的癌症，其转移过程中细胞外基质的重塑起着重要作用。
本文将探讨肝癌细胞外基质重塑与转移的相关机制。
一、肝癌细胞外基质的构成肝癌细胞外基质由多种成分组成，其中胶原蛋白是最主要的成分之一，它在肝癌的形成和发展过程中扮演着重要角色。
除胶原蛋白外，纤维连接蛋白、基质金属蛋白酶和粘附分子等也参与了细胞外基质的构建和维持。
二、肝癌细胞外基质的重塑在肝癌发展过程中，细胞外基质会发生重塑现象，尤其是癌细胞周围的基质发生了明显的变化。
这种重塑主要表现为基质成分的改变、基质的刚度增加和基质的病理性改变等。
1. 基质成分的改变肝癌细胞外基质中的成分会发生变化，例如胶原蛋白的增加和分子构型的改变。
研究发现，肝癌组织中的胶原蛋白含量明显增加，而且其在细胞外基质中的排列方式也发生了改变，过度聚集的胶原蛋白会导致细胞外基质刚度增加，从而增强肿瘤细胞的浸润和侵袭能力。
2. 基质的刚度增加肝癌细胞外基质的刚度增加是由于胶原蛋白等成分的改变导致的。
细胞外基质的刚度与肿瘤细胞的生物学行为密切相关，当基质刚度增加时，肝癌细胞会更容易侵入周围组织并进一步转移。
因此，针对细胞外基质的刚度调控可能有助于阻断肝癌的转移过程。
3. 基质的病理性改变肝癌细胞周围的细胞外基质还可能发生病理性改变。
一些研究发现，肿瘤相关基质（tumor-associated matrix）的形成与肝癌的进展和预后密切相关。
肿瘤相关基质会增强肿瘤细胞的侵袭和转移能力，并且还能调节肿瘤免疫反应和血管生成等生物学过程。
三、肝癌细胞外基质重塑与转移的机制肝癌细胞外基质的重塑与肝癌细胞的转移密切相关，涉及多种分子和信号途径的调控。
1.基质金属蛋白酶参与的降解基质金属蛋白酶（matrix metalloproteinases，MMPs）是一类能够降解细胞外基质的酶。
基质金属蛋白酶_识别位点_概述说明以及解释
基质金属蛋白酶识别位点概述说明以及解释1. 引言1.1 概述:基质金属蛋白酶（matrix metalloproteinases, MMPs）是一类具有重要生物学功能的酶家族，广泛存在于人体和其他生物体内。
它们在细胞外基质的代谢、细胞迁移、炎症反应、组织修复等多种生物过程中扮演着关键角色。
基质金属蛋白酶通过降解与调控胶原蛋白、纤维连接蛋白等基质成分的结构，参与了许多疾病的发展和进展，如肿瘤转移、心脏病变以及风湿性关节炎等。
1.2 文章结构:本文将依次介绍基质金属蛋白酶的概述、识别位点的重要性以及该领域的研究方法和技术。
首先，我们将对基质金属蛋白酶进行分类定义，并探讨它们在结构和功能特点上的差异。
随后，我们将深入讨论基质金属蛋白酶在生理和病理过程中识别位点的意义，并介绍一些重要识别位点的例子和作用机制。
接下来，我们将详细介绍实验室技术手段、生物信息学分析方法以及基于计算模型预测识别位点的方法。
最后，我们将对基质金属蛋白酶识别位点研究现状进行总结归纳，并展望未来可能的研究方向和应用前景。
1.3 目的:本文旨在全面深入地探讨基质金属蛋白酶识别位点的概述、意义以及相关研究方法和技术。
通过对该领域的综述，我们希望能够提高人们对基质金属蛋白酶与其识别位点之间关系的理解，并促进该领域的进一步研究和应用。
同时，我们也期望为未来开展相关疾病治疗、药物设计等方面的工作提供参考和借鉴。
2. 基质金属蛋白酶概述：2.1 定义与分类：基质金属蛋白酶是一类广泛存在于细胞内和细胞外的酶，其特点在于能够催化多种蛋白质的降解和修饰过程。
它们主要通过断裂或修改细胞外基质中的蛋白质分子，从而参与了许多重要的生物学过程，如组织发育、炎症反应和肿瘤转移等。
基质金属蛋白酶按照结构、底物特异性以及金属离子需求等方面进行了分类，包括胶原酶、凝血酶样蛋白酶、凝血素样活化剂等多个亚族。
2.2 结构与功能特点：基质金属蛋白酶通常由一个完整的蛋白结构域组成，该结构域含有保守性高的催化位点和底物结合位点。
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细胞外基质中金属蛋白酶的结构和功能
细胞外基质（ECM）是一种薄而致密的自然基质，存在于组织和器官之间。
它由众多的蛋白质分子构成，包括胶原蛋白、弹性蛋白、纤维连接蛋白、荧光素等。
ECM不仅是细胞外的物理结构支持，还在许多生理或病理情况下调节着细胞的形态、迁移和增殖。
金属蛋白酶（MMP）是ECM中的一种重要酶类，负责去除并修剪ECM，以便于细胞的迁移和生长。
MMP是一类结构相似、功能类似的锌蛋白酶。
它们通常由一个信号序列和一
个活性亚基组成，分子量在50 kDa以上。
它们的活性部位包括三种氨基酸残基：
谷氨酰胺（Glu）、丝氨酸（Ser）和脯氨酸（Pro）。
活性物质中的锌离子被一个
固定的组方位于该酶的中心，其帮助成员酶与底物相结合，在酶反应中发挥催化作用。
MMP的活性受到许多不同的组织学和生物化学因素的调节。
特别是组织细胞
来源的生长因子，如胰高血糖素、信息素和干扰素，以及天然组织抑制物和抗血管生成因子等。
MMP主要作用于ECM上的基质分子，包括胶原、卵剂素、纤维网蛋白、纤维素等。
MMP的作用主要由其底物专属性决定。
MMP-1、MMP-2、MMP-3、MMP-7、MMP-8、MMP-9和MMP-12主要降解胶原蛋白；MMP-9和MMP-20降解卵剂
素和纤维连结蛋白；MMP-1、MMP-3和MMP-9降解纤维素；而MMP-14则主要
作用于银联素-1和银联素-2等区分过程的微纤蛋白。
这种底物专属性使得MMP能
够在特定的细胞类型、生物修复过程和病理情况中表现出差异化特点。
MMP可能与许多与肿瘤和心血管疾病有关的过程相关。
例如，在不同层面上，MMP在肿瘤发生、肿瘤生长、肺、乳房和黏膜颈部癌细胞的迁移和侵袭等方面发
挥了重要作用。
总的来说，ECM是一个动态的、复杂的网络，由许多互补的分子和结构因素
组成。
MMP是这个网络中的一个重要组成部分，通过修剪和去除ECM中的分子，
维持其反应性和可塑性。
同时，MMP在生理和病理方面都发挥了重要的作用，因此，对MMP的结构和功能的深入了解是值得进行的进一步研究的方向。