How does sulfhydryl group of cysteine participate in the following reaction?
Thiol proteases cleave peptide bonds by a mechanism similar to that of serine proteases, such as trypsin and chymotrypsin, but they contain cysteine instead of serine.
A. It participates in substrate binding, and thereby helps determining the substrate specificity of the enzyme B. It react covalently with the side chain of an acidic amino acid residue in the substrate C. It attacks the C=O portion of a peptide bond, and forms a thioester with it D. It relays electrons to the peptide bond of the substrate, thereby facilitating the formation of a tetrahedral intermediate E. It forms a transient disulfide bond with a cysteine side chain of the substrate