Studies on the specificity of protaminase

Abstract The action of protaminase liberates all C-terminal arginine and lysines from the tryptic digest of α-lactalbumin. Protaminase is inert toward the chymotryptic digest of α-lactalbumin as carboxypeptidase is nonreactive to the tryptic digest of this protein. In accordance with the specificity of carboxypeptidase, the addition of this enzyme to a chymotryptic digest of α-lactalbumin effected a rapid liberation of all the C-terminal tyrosine and phenylalanine together with other amino acids. Protaminase hydrolyzes peptides with C-terminal arginine, lysine, and S -(β-aminoethyl)cysteine, and its action is confined to the liberation of these amino acids. Protaminase and carboxypeptidase-B are identical enzymes.