Cysteine/Serine proteases

Cysteine/serine proteases in viruses act in the processing of polyproteins, maturation of capsid/virion or modulation of host immune response. They are a type of enzyme that catalyze the hydrolysis of peptide bonds and use a cysteine or serine residue in their active site to perform this hydrolysis reaction.

(Wikipedia:Serine peptidase, Cysteine peptidase)

Enzymatic reaction:

• Ser-endopeptidase EC.3.4.21.-
• Cys-endopeptidase EC.3.4.22.-

Mechanism The active site of a cysteine/serine protease consists of three key amino acids: cysteine/serine, histidine, and aspartate. Together, these residues form a catalytic triad that facilitates the cleavage of peptide bonds in proteins. The cysteine/serine residue acts as a nucleophile, attacking the carbonyl carbon of the peptide bond, while the histidine and aspartate residues assist the process by stabilizing the reaction intermediates.

Cysteine proteases