Matrix metalloproteinase

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Matrix metalloproteinase
Identifiers
SymbolMMP
Pfam clan CL0126
InterPro IPR021190
Membranome 317

Matrix metalloproteinases (MMPs), also known as matrix metallopeptidases or matrixins, are metalloproteinases that are calcium-dependent zinc-containing endopeptidases; [1] other family members are adamalysins, serralysins, and astacins. The MMPs belong to a larger family of proteases known as the metzincin superfamily. [2]

Contents

Collectively, these enzymes are capable of degrading all kinds of extracellular matrix proteins, but also can process a number of bioactive molecules. They are known to be involved in the cleavage of cell surface receptors, the release of apoptotic ligands (such as the FAS ligand), and chemokine/cytokine inactivation. [3] MMPs are also thought to play a major role in cell behaviors such as cell proliferation, migration (adhesion/dispersion), differentiation, angiogenesis, apoptosis, and host defense.

They were first described in vertebrates in 1962, [4] including humans, but have since been found in invertebrates and plants. They are distinguished from other endopeptidases by their dependence on metal ions as cofactors, their ability to degrade extracellular matrix, and their specific evolutionary DNA sequence.

History

MMPs were described initially by Jerome Gross and Charles Lapiere in 1962, who observed enzymatic activity (collagen triple helix degradation) during tadpole tail metamorphosis (by placing a tadpole tail in a collagen matrix plate). [5] Therefore, the enzyme was named interstitial collagenase (MMP-1).

Later, it was purified from human skin (1968), [6] and was recognized to be synthesized as a zymogen. [7]

The "cysteine switch" was described in 1990. [8]

Structure

The MMPs have a common domain structure. The three common domains are the pro-peptide, the catalytic domain, and the haemopexin-like C-terminal domain, which is linked to the catalytic domain by a flexible hinge region. [2]

The pro-peptide

The MMPs are initially synthesized as inactive zymogens with a pro-peptide domain that must be removed before the enzyme is active. The pro-peptide domain is part of the "cysteine switch." This contains a conserved cysteine residue that interacts with the zinc in the active site and prevents binding and cleavage of the substrate, keeping the enzyme in an inactive form. In the majority of the MMPs, the cysteine residue is in the conserved sequence PRCGxPD. Some MMPs have a prohormone convertase cleavage site (Furin-like) as part of this domain, which, when cleaved, activates the enzyme. MMP-23A and MMP-23B include a transmembrane segment in this domain. [9]

The catalytic domain

X-ray crystallographic structures of several MMP catalytic domains have shown that this domain is an oblate sphere measuring 35 x 30 x 30 Å (3.5 × 3 x 3 nm). The active site is a 20 Å (2 nm) groove that runs across the catalytic domain. In the part of the catalytic domain forming the active site there is a catalytically important Zn 2+ ion, which is bound by three histidine residues found in the conserved sequence HExxHxxGxxH. Hence, this sequence is a zinc-binding motif.

The gelatinases, such as MMP-2, incorporate Fibronectin type II modules inserted immediately before in the zinc-binding motif in the catalytic domain. [10]

The hinge region

The catalytic domain is connected to the C-terminal domain by a flexible hinge or linker region. This is up to 75 amino acids long, and has no determinable structure.

The hemopexin-like C-terminal domain

The hemopexin-like C-terminal domain of MMP9 PDB 1itv Protein MMP9 PDB 1itv.png
The hemopexin-like C-terminal domain of MMP9 PDB 1itv

The C-terminal domain has structural similarities to the serum protein hemopexin. It has a four-bladed β-propeller structure. β-Propeller structures provide a large flat surface that is thought to be involved in protein-protein interactions. This determines substrate specificity and is the site for interaction with TIMP's (tissue inhibitor of metalloproteinases). The hemopexin-like domain is absent in MMP-7, MMP-23, MMP-26, and the plant and nematode. The membrane-bound MMPs (MT-MMPs) are anchored to the plasma membrane via a transmembrane or a GPI-anchoring domain.

Catalytic mechanism

There are three catalytic mechanisms published.

Classification

Functional classification of matrix metalloproteinases. Matrix Metalloproteinases.png
Functional classification of matrix metalloproteinases.

The MMPs can be subdivided in different ways.

Evolutionary

Use of bioinformatic methods to compare the primary sequences of the MMPs suggest the following evolutionary groupings of the MMPs:

Analysis of the catalytic domains in isolation suggests that the catalytic domains evolved further once the major groups had differentiated, as is also indicated by the substrate specificities of the enzymes.

Functional

The most commonly used groupings (by researchers in MMP biology) are based partly on historical assessment of the substrate specificity of the MMP and partly on the cellular localization of the MMP. These groups are the collagenases, the gelatinases, the stromelysins, and the membrane-type MMPs (MT-MMPs).

However, it is becoming increasingly clear that these divisions are somewhat artificial as there are a number of MMPs that do not fit into any of the traditional groups.

Genes

GeneNameAliasesLocationDescription
MMP1 Interstitial collagenaseCLG, CLGNsecretedSubstrates include Col I, II, III, VII, VIII, X, gelatin
MMP2 Gelatinase-A, 72 kDa gelatinasesecretedSubstrates include Gelatin, Col I, II, III, IV, Vii, X
MMP3 Stromelysin 1CHDS6, MMP-3, SL-1, STMY, STMY1, STR1secretedSubstrates include Col II, IV, IX, X, XI, gelatin
MMP7 Matrilysin, PUMP 1MMP-7, MPSL1, PUMP-1secretedmembrane associated through binding to cholesterol sulfate in cell membranes, substrates include: fibronectin, laminin, Col IV, gelatin
MMP8 Neutrophil collagenaseCLG1, HNC, MMP-8, PMNL-CLsecretedSubstrates include Col I, II, III, VII, VIII, X, aggrecan, gelatin
MMP9 Gelatinase-B, 92 kDa gelatinaseCLG4B, GELB, MANDP2, MMP-9secretedSubstrates include Gelatin, Col IV, V
MMP10 Stromelysin 2SL-2, STMY2secretedSubstrates include Col IV, laminin, fibronectin, elastin
MMP11 Stromelysin 3SL-3, ST3, STMY3secretedMMP-11 shows more similarity to the MT-MMPs, is convertase-activatable and is secreted therefore usually associated to convertase-activatable MMPs. Substrates include Col IV, fibronectin, laminin, aggrecan
MMP12 Macrophage metalloelastaseHME, ME, MME, MMP-12secretedSubstrates include elastin, fibronectin, Col IV
MMP13 Collagenase 3CLG3, MANDP1, MMP-13secretedSubstrates include Col I, II, III, IV, IX, X, XIV, gelatin
MMP14 MT1-MMPMMP-14, MMP-X1, MT-MMP, MT-MMP 1, MT1-MMP, MT1MMP, MTMMP1, WNCHRSmembrane-associatedtype-I transmembrane MMP; substrates include gelatin, fibronectin, laminin
MMP15 MT2-MMPMT2-MMP, MTMMP2, SMCP-2, MMP-15, MT2MMPmembrane-associatedtype-I transmembrane MMP; substrates include gelatin, fibronectin, laminin
MMP16 MT3-MMPC8orf57, MMP-X2, MT-MMP2, MT-MMP3, MT3-MMPmembrane-associatedtype-I transmembrane MMP; substrates include gelatin, fibronectin, laminin
MMP17 MT4-MMPMT4-MMP, MMP-17, MT4MMP, MTMMP4membrane-associated glycosyl phosphatidylinositol-attached; substrates include fibrinogen, fibrin
MMP18Collagenase 4, xcol4, xenopus collagenaseNo known human orthologue
MMP19 RASI-1, occasionally referred to as stromelysin-4MMP18, RASI-1, CODA
MMP20 EnamelysinAI2A2, MMP-20secreted
MMP21 X-MMPMMP-21, HTX7secreted
MMP23A CA-MMPmembrane-associatedtype-II transmembrane cysteine array
MMP23B MIFR, MIFR-1, MMP22, MMP23Amembrane-associatedtype-II transmembrane cysteine array
MMP24 MT5-MMPMMP-24, MMP25, MT-MMP 5, MT-MMP5, MT5-MMP, MT5MMP, MTMMP5membrane-associatedtype-I transmembrane MMP
MMP25 MT6-MMPMMP-25, MMP20, MMP20A, MMPL1, MT-MMP 6, MT-MMP6, MT6-MMP, MT6MMP, MTMMP6membrane-associated glycosyl phosphatidylinositol-attached
MMP26 Matrilysin-2, endometase
MMP27 MMP-22, C-MMPMMP-27
MMP28 EpilysinEPILYSIN, MM28, MMP-25, MMP-28, MMP25secretedDiscovered in 2001 and given its name due to have been discovered in human keratinocytes. Unlike other MMPs this enzyme is constitutivley expressed in many tissues (Highly expressed in testis and at lower levels in lung, heart, brain, colon, intestine, placenta, salivary glands, uterus, skin). A threonine replaces proline in its cysteine switch (PRCGVTD). [14]

Matrix metalloproteinases combines with the metal binding protein, metallothionine; thus helping in metal binding mechanism.

Function

The MMPs play an important role in tissue remodeling associated with various physiological or pathological processes such as morphogenesis, angiogenesis, tissue repair, cirrhosis, arthritis, and metastasis. MMP-2 and MMP-9 are thought to be important in metastasis. MMP-1 is thought to be important in rheumatoid arthritis and osteoarthritis. Recent data suggests active role of MMPs in the pathogenesis of Aortic Aneurysm. Excess MMPs degrade the structural proteins of the aortic wall. Disregulation of the balance between MMPs and TIMPs is also a characteristic of acute and chronic cardiovascular diseases. [15]

Activation

mutual activation of MMPs Mutual MMP activation.svg
mutual activation of MMPs

All MMPs are synthesized in the latent form (Zymogen). They are secreted as proenzymes and require extracellular activation. They can be activated in vitro by many mechanisms including organomercurials, chaotropic agents, and other proteases.

Inhibitors

The MMPs are inhibited by specific endogenous tissue inhibitor of metalloproteinases (TIMPs), which comprise a family of four protease inhibitors: TIMP-1, TIMP-2, TIMP-3, and TIMP-4.

Synthetic inhibitors generally contain a chelating group that binds the catalytic zinc atom at the MMP active site tightly. Common chelating groups include hydroxamates, carboxylates, thiols, and phosphinyls. Hydroxymates are particularly potent inhibitors of MMPs and other zinc-dependent enzymes, due to their bidentate chelation of the zinc atom. Other substituents of these inhibitors are usually designed to interact with various binding pockets on the MMP of interest, making the inhibitor more or less specific for given MMPs. [2]

Pharmacology

Doxycycline, at subantimicrobial doses, inhibits MMP activity, and has been used in various experimental systems for this purpose, such as for recalcitrant recurrent corneal erosions. It is used clinically for the treatment of periodontal disease and is the only MMP inhibitor that is widely available clinically. It is sold under the trade name Periostat by the company CollaGenex. Minocycline, another tetracycline antibiotic, has also been shown to inhibit MMP activity.

A number of rationally designed MMP inhibitors have shown some promise in the treatment of pathologies that MMPs are suspected to be involved in (see above). However, most of these, such as marimastat (BB-2516), a broad-spectrum MMP inhibitor, and cipemastat (Ro 32-3555), an MMP-1 selective inhibitor, have performed poorly in clinical trials. The failure of Marimastat was partially responsible for the folding of British Biotech, which developed it. The failure of these drugs has been due largely to toxicity (in particular, musculo-skeletal toxicity in the case of broad spectrum inhibitors) and failure to show expected results (in the case of trocade, promising results in rabbit arthritis models were not replicated in human trials). The reasons behind the largely disappointing clinical results of MMP inhibitors is unclear, especially in light of their activity in animal models.

See also

Related Research Articles

<span class="mw-page-title-main">Metalloproteinase</span> Type of enzyme

A metalloproteinase, or metalloprotease, is any protease enzyme whose catalytic mechanism involves a metal. An example is ADAM12 which plays a significant role in the fusion of muscle cells during embryo development, in a process known as myogenesis.

Gelatinases are enzymes capable of degrading gelatin through hydrolysis, playing a major role in degradation of extracellular matrix and tissue remodeling. Gelatinases are a type of matrix metalloproteinase (MMP), a family of enzymes that depend on zinc as a cofactor and can break down parts of the extracellular matrix. MMPs have multiple subgroups, including gelatinase A and gelatinase B. Gelatinases are assigned a variety of Enzyme Commission numbers: gelatinase A uses 3.4.24.24, and gelatinase B uses 3.4.24.35, in which the first three numbers are same. The first digit, 3, is the class. Class 3 enzymes are hydrolases, enzymes that catalyze hydrolysis reactions, that is, they cleave bonds in presence of water. The next digit represents sub-class 4, or proteases, which are enzymes who hydrolyze peptide bonds in proteins. The next number is the sub-subclass of 24, which consists of metalloendopeptidases which contain metal ions in their active sites, in this case zinc, which help in cleaving peptide bonds. The last part of the EC number is the serial number, identifying specific enzymes within a sub-subclass. 24 represents gelatinase A, which is a metalloproteinase that breaks down gelatin and collagen, while 35 represents gelatinase B, which hydrolyzes peptide bonds.

Collagenases are enzymes that break the peptide bonds in collagen. They assist in destroying extracellular structures in the pathogenesis of bacteria such as Clostridium. They are considered a virulence factor, facilitating the spread of gas gangrene. They normally target the connective tissue in muscle cells and other body organs.

<span class="mw-page-title-main">Carboxypeptidase A</span>

Carboxypeptidase A usually refers to the pancreatic exopeptidase that hydrolyzes peptide bonds of C-terminal residues with aromatic or aliphatic side-chains. Most scientists in the field now refer to this enzyme as CPA1, and to a related pancreatic carboxypeptidase as CPA2.

<span class="mw-page-title-main">MMP9</span> Protein-coding gene in the species Homo sapiens

Matrix metalloproteinase-9 (MMP-9), also known as 92 kDa type IV collagenase, 92 kDa gelatinase or gelatinase B (GELB), is a matrixin, a class of enzymes that belong to the zinc-metalloproteinases family involved in the degradation of the extracellular matrix. In humans the MMP9 gene encodes for a signal peptide, a propeptide, a catalytic domain with inserted three repeats of fibronectin type II domain followed by a C-terminal hemopexin-like domain.

<span class="mw-page-title-main">MMP2</span> Protein-coding gene in the species Homo sapiens

72 kDa type IV collagenase also known as matrix metalloproteinase-2 (MMP-2) and gelatinase A is an enzyme that in humans is encoded by the MMP2 gene. The MMP2 gene is located on chromosome 16 at position 12.2.

Interstitial collagenase, also known as fibroblast collagenase and matrix metalloproteinase-1 (MMP-1), is an enzyme that in humans is encoded by the MMP1 gene. The gene is part of a cluster of MMP genes which localize to chromosome 11q22.3. MMP-1 was the first vertebrate collagenase both purified to homogeneity as a protein, and cloned as a cDNA. MMP-1 has an estimated molecular mass of 54 kDa.

<span class="mw-page-title-main">MMP3</span>

Stromelysin-1 also known as matrix metalloproteinase-3 (MMP-3) is an enzyme that in humans is encoded by the MMP3 gene. The MMP3 gene is part of a cluster of MMP genes which localize to chromosome 11q22.3. MMP-3 has an estimated molecular weight of 54 kDa.

<span class="mw-page-title-main">TIMP2</span> Protein-coding gene in the species Homo sapiens

Tissue inhibitor of metalloproteinases 2 (TIMP2) is a gene and a corresponding protein. The gene is a member of the TIMP gene family. The protein is thought to be a metastasis suppressor.

<span class="mw-page-title-main">MMP7</span> Protein-coding gene in humans

Matrilysin also known as matrix metalloproteinase-7 (MMP-7), pump-1 protease (PUMP-1), or uterine metalloproteinase is an enzyme in humans that is encoded by the MMP7 gene. The enzyme has also been known as matrin, putative metalloproteinase-1, matrix metalloproteinase pump 1, PUMP-1 proteinase, PUMP, metalloproteinase pump-1, putative metalloproteinase, MMP). Human MMP-7 has a molecular weight around 30 kDa.

<span class="mw-page-title-main">Matrix metallopeptidase 13</span> Protein-coding gene in the species Homo sapiens

Collagenase 3 is an enzyme that in humans is encoded by the MMP13 gene. It is a member of the matrix metalloproteinase (MMP) family. Like most MMPs, it is secreted as an inactive pro-form. MMP-13 has a predicted molecular weight around 54 kDa. It is activated once the pro-domain is cleaved, leaving an active enzyme composed of the catalytic domain and the hemopexin-like domain PDB: 1PEX​. Although the actual mechanism has not been described, the hemopexin domain participates in collagen degradation, the catalytic domain alone being particularly inefficient in collagen degradation. During embryonic development, MMP-13 is expressed in the skeleton as required for restructuring the collagen matrix for bone mineralization. In pathological situations it is highly overexpressed; this occurs in human carcinomas, rheumatoid arthritis and osteoarthritis.

<span class="mw-page-title-main">Matrix metallopeptidase 12</span> Enzyme involved in breakdown of extracellular matrix, encoded for by the MMP12 gene in humans

Matrix metalloproteinase-12 (MMP-12) also known as macrophage metalloelastase (MME) or macrophage elastase (ME) is an enzyme that in humans is encoded by the MMP12 gene.

<span class="mw-page-title-main">MMP26</span> Protein-coding gene in the species Homo sapiens

Matrix metalloproteinase-26 also known as matrilysin-2 and endometase is an enzyme that in humans is encoded by the MMP26 gene.

<span class="mw-page-title-main">TIMP4</span> Protein-coding gene in the species Homo sapiens

Metalloproteinase inhibitor 4 is an enzyme that in humans is encoded by the TIMP4 gene.

<span class="mw-page-title-main">MMP8</span> Protein-coding gene in the species Homo sapiens

Neutrophil collagenase, also known as matrix metalloproteinase-8 (MMP-8) or PMNL collagenase (MNL-CL), is a collagen cleaving enzyme which is present in the connective tissue of most mammals. In humans, the MMP-8 protein is encoded by the MMP8 gene. The gene is part of a cluster of MMP genes which localize to chromosome 11q22.3. Most MMP's are secreted as inactive proproteins which are activated when cleaved by extracellular proteinases. However, the enzyme encoded by this gene is stored in secondary granules within neutrophils and is activated by autolytic cleavage.

Metalloprotease inhibitors are cellular inhibitors of the Matrix metalloproteinases (MMPs). MMPs belong to a family of zinc-dependent neutral endopeptidases. These enzymes have the ability to break down connective tissue. The expression of MMPs is increased in various pathological conditions like inflammatory conditions, metabolic bone disease, to cancer invasion, metastasis and angiogenesis. Examples of diseases are periodontitis, hepatitis, glomerulonephritis, atherosclerosis, emphysema, asthma, autoimmune disorders of skin and dermal photoaging, rheumatoid arthritis, osteoarthritis, multiple sclerosis, Alzheimer's disease, chronic ulcerations, uterine involution, corneal epithelial defects, bone resorption and tumor progression and metastasis. Due to the role of MMPs in pathological conditions, inhibitors of MMPs may have therapeutic potential. Several other proteins have similar inhibitory effects, however none as effective. They might have other biological activities which have yet been fully characterised.

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<span class="mw-page-title-main">Peptidoglycan binding domain</span> Class of protein structural domains

Peptidoglycan binding domains have a general peptidoglycan binding function and a common core structure consisting of a closed, three-helical bundle with a left-handed twist. It is found at the N or C terminus of a variety of enzymes involved in bacterial cell wall degradation. Examples are:

The hemopexin family is a family of evolutionarily related proteins. Hemopexin-like repeats occur in vitronectin and some matrix metalloproteinases family (matrixins). The HX repeats of some matrixins bind tissue inhibitor of metallopeptidases (TIMPs).

Plant matrix metalloproteinases are metalloproteins and zinc enzymes found in plants.

References

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Synergistic effect of stromelysin-1 (matrix metalloproteinase-3) promoter (-1171 5A->6A) polymorphism in oral submucous fibrosis and head and neck lesions.Chaudhary AK, Singh M, Bharti AC, Singh M, Shukla S, Singh AK, Mehrotra R. BMC Cancer. 2010 Jul 14;10:369.