Serine protease

Structure of trypsin, a serine protease.

Serine proteases are hydrolases that degrade peptide bonds of peptides and proteins and which have at their active site a serine amino acid essential for enzymatic catalysis. This class of enzymes (classified as EC | 3.4.21) includes trypsin, chymotrypsin, subtilisin granzyme and others.

Serine proteases cut the polypeptide chain on the carboxyl side of specific amino acids, that is, they recognize sequences in the primary structure. For example, trypsin cuts on the carboxylate side of basic residues such as lysine or arginine, while chymotrypsin cleaves alongside hydrophobic residues such as phenylalanine.

There is some structural homogeneity in terms of structural conformation of serine proteases, suggesting an evolutionary relationship between them. For example, serine proteases always possess a catalytic triad of aspartate, histidine and serine located in the catalytic crack of the active site. In addition, these enzymes always have a "pocket" located near the serine of the active site. In the case of trypsin, this pocket allows it to capture and maintain basic amino acids (positively charged), because the enzyme has in that place the carboxyl group of the side chain of an aspartic acid; that is, the presence of an acid residue in the pocket is that which confers its specificity to trypsin, the affinity for the cut in basic amino acids of the target proteins, amino acids that interact by electrostatic interaction with the acidic group of the pocket. p>

Systematic listing of Serine Proteases on the ExPassy page

wiki