serine-type endopeptidase activity

Definition

Target type: molecularfunction

Catalysis of the hydrolysis of internal, alpha-peptide bonds in a polypeptide chain by a catalytic mechanism that involves a catalytic triad consisting of a serine nucleophile that is activated by a proton relay involving an acidic residue (e.g. aspartate or glutamate) and a basic residue (usually histidine). [GOC:mah, https://www.ebi.ac.uk/merops/about/glossary.shtml#CATTYPE]

Serine-type endopeptidases are a large and diverse family of enzymes that catalyze the hydrolysis of peptide bonds within protein molecules. They are characterized by the presence of a catalytic triad consisting of a serine residue, a histidine residue, and an aspartic acid residue. These residues work together to facilitate the cleavage of the peptide bond.

The catalytic mechanism of serine-type endopeptidases involves a two-step process:

1. **Nucleophilic attack:** The hydroxyl group of the serine residue in the active site attacks the carbonyl carbon of the peptide bond, forming a covalent intermediate known as an acyl-enzyme. This step is facilitated by the histidine residue, which acts as a base to deprotonate the serine hydroxyl group, making it a better nucleophile.

2. **Hydrolysis:** Water molecules then attack the carbonyl carbon of the acyl-enzyme intermediate, breaking the covalent bond and releasing the carboxyl terminus of the peptide. This step is facilitated by the aspartic acid residue, which acts as an acid to protonate the water molecule, making it a better nucleophile.

The serine-type endopeptidases play a crucial role in a wide range of biological processes, including protein degradation, signal transduction, and immune response. They are involved in the breakdown of proteins during digestion, the activation of enzymes and hormones, and the regulation of inflammation.

Some examples of serine-type endopeptidases include:

* **Trypsin:** A digestive enzyme that breaks down proteins in the small intestine.
* **Chymotrypsin:** Another digestive enzyme that cleaves peptide bonds adjacent to aromatic amino acids.
* **Elastase:** An enzyme that breaks down elastin, a protein found in connective tissues.
* **Thrombin:** An enzyme involved in blood clotting.
* **Caspases:** A family of enzymes involved in apoptosis (programmed cell death).

The activity of serine-type endopeptidases is highly specific and can be regulated by various factors, including pH, temperature, and the presence of inhibitors. These enzymes are often targeted by drugs to treat diseases, such as cancer and cardiovascular disease.'
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Proteins (112)

Compounds (700)