BIOC 303 Chapter : Proteases Sept08.pdf
Document Summary
Release of amino acids from proteins by proteolysis. Amino group reactions facilitate movement of amino groups between structures or net deamination. Urea cycle and nitrogen excretion as ammonia and urea: metabolism of carbon structures of amino acids involves a range of pathways for the specific structures. Note the basic peptide bond cleavage reaction addition of water across the amide bond. Peptide bonds are hydrolyzed by a broad range of proteases (also called proteinases). Based on the role of specific active site amino acids, six major families of proteases are designated as cysteine-, threonine-, serine-, aspartate-, glutamate- and metallo-proteases. In the first three groups, activated cysteine, threonine or serine residues serve as nucleophiles to initiate peptide bond cleavage (see the mechanism of the chymotrypsin reaction). In the latter three groups, aspartate, glutamate or a metal ion activate a water molecule to serve as the nucleophile. Cysteine, serine and metallo- proteases together account for over 500 human proteases.
