Carboxypeptidase
From Wikipedia, the free encyclopedia
Carboxypeptidase (EC number 3.4.16 - 3.4.18) is an enzyme that hydrolyzes the carboxy-terminal (C-terminal) end of a peptide bond. Humans, animals, and plants contain several types of carboxypeptidases with diverse functions ranging from catabolism to protein maturation.
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[edit] Functions
The first carboxypeptidases studied were those involved in the digestion of food (pancreatic carboxypeptidases A1, A2, and B). However, most of the known carboxypeptidases are not involved in catabolism; they help to mature proteins or regulate biological processes. For example, the biosynthesis of neuroendocrine peptides such as insulin requires a carboxypeptidase. Carboxypeptidases also function in blood clotting, growth factor production, wound healing, reproduction, and many other processes.
[edit] Classification
[edit] By active site mechanism
Carboxypeptidases are usually classified into one of several families based on their active site mechanism.
- Enzymes that use a metal in the active site are called "metallo-carboxypeptidases".
- Other carboxypeptidases that use active site serine residues are called "serine carboxypeptidases".
- Those that use an active site cysteine are called "cysteine carboxypeptidase" (or "thiol carboxypeptidases").
These names do not refer to the selectivity of the amino acid that is cleaved.
[edit] By substrate preference
Another classification system for carboxypeptidases refers to their substrate preference.
- In this classification system, carboxypeptidases that have a stronger preference for those amino acids containing aromatic or branched hydrocarbon chains are called carboxypeptidase A (A for aromatic/aliphatic).
- Carboxypeptidases that cleave positively charged amino acids (arginine, lysine) are called carboxypeptidase B (B for basic).
A metallo-carboxypeptidase that cleaves a C-terminal glutamate from the peptide N-acetyl-L-aspartyl-L-glutamate is called "glutamate carboxypeptidase".
A serine carboxypeptidase that cleaves the C-terminal residue from peptides containing the sequence -Pro-Xaa (Pro is proline, Xaa is any amino acid on the C-terminus of a peptide) is called "prolyl carboxypeptidase".
[edit] Activation
Some, but not all, carboxypeptidases are initially produced in an inactive form; this precursor form is referred to as a procarboxypeptidase. In the case of pancreatic carboxypeptidase A, the inactive zymogen form, pro-carboxypeptidase A, is converted to its active form - carboxypeptidase A - by the enzyme enteropeptidase. This mechanism ensures that the cells wherein pro-carboxypeptidase A is produced are not themselves digested.
[edit] See also
[edit] See also
- Enzyme category EC number 3.4
- Thrombin-activatable fibrinolysis inhibitor aka plasma carboxypeptidase B2
- bacterial transpeptidase, an alanine carboxypeptidase
- bradykinin is broken down among other enzymes by carboxypeptidase N
- D-Ala carboxypeptidase is a penicillin binding proteins
- Phenylalanine might inhibit carboxypeptidase A
[edit] External links
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