Matrix metalloproteinase-20 (MMP-20) also known as enamel metalloproteinase or enamelysin is an
enzyme
An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...
that in humans is encoded by the ''MMP20''
gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
.
Function
Proteins of the matrix metalloproteinase (
MMP) family are involved in the breakdown of
extracellular matrix
In biology, the extracellular matrix (ECM), also called intercellular matrix (ICM), is a network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide structural and bio ...
in normal physiological processes, such as embryonic development, reproduction, and tissue remodeling, as well as in disease processes, such as arthritis and metastasis. Most MMP's are secreted as inactive proproteins which are activated when cleaved by extracellular
proteinase
A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalyzes proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the formation of new protein products. They do ...
s.
MMP-20, also known as enamelysin, appears to be the only MMP that is tooth-specific and it is expressed by cells of different developmental origin (i.e. epithelial
ameloblast
Ameloblasts are cells present only during tooth development that deposit tooth enamel, which is the hard outermost layer of the tooth forming the surface of the crown.
Structure
Each ameloblast is a columnar cell approximately 4 micrometers in ...
s and mesenchymal
odontoblast
In vertebrates, an odontoblast is a cell of neural crest origin that is part of the outer surface of the dental pulp, and whose biological function is dentinogenesis, which is the formation of dentin, the substance beneath the tooth enamel on t ...
s).
Clinical significance
The human MMP-20 gene contains 10 exons and is part of a cluster of matrix metalloproteinase genes that localize to human chromosome 11q22.3.
A mutation in this gene, which alters the normal splice pattern and results in premature termination of the encoded protein, has been associated with
amelogenesis imperfecta
Amelogenesis imperfecta (AI) is a congenital disorder which presents with a rare abnormal formation of the Tooth enamel, enamel or external layer of the crown of teeth, unrelated to any systemic or generalized conditions. Enamel is composed mostly ...
. Enamel in the absence of MMP-20 is hypoplastic (thin), contains less mineral (only one-third as much total mineral as wild type), and contains more protein and water. In general, MMP-20 functions in enamel are to cleave enamel matrix proteins at specific cleavage sites.
References
Further reading
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External links
* The
MEROPS
MEROPS is an online database for peptidases (also known as proteases, proteinases and proteolytic enzymes) and their inhibitors. The classification scheme for peptidases was published by Rawlings & Barrett in 1993, and that for protein inhibito ...
online database for peptidases and their inhibitors
M10.019*
Matrix metalloproteinases
EC 3.4.24
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