LYTIC ENZYMES OF SORANGIUM SP.: A COMPARISON OF THE PROTEOLYTIC PROPERTIES OF THE α- AND β-LYTIC PROTEASES

Abstract

The proteolytic properties of the α- and β-lytic proteases of a species of Sorangium were compared. Neither enzyme showed evidence of aminopeptidase, carboxypeptidase, or amidase activity in tests with a series of peptides and substituted amino acids at pH 5.2, 7.2, and 9.0. Neither enzyme showed evidence of esterase activity towards N-benzoyl-L-arginine methyl ester at pH 6.8. Hydrolysis of the A chain of oxidized insulin at pH 9 slows down markedly when the α-enzyme has cleaved the chain once; the initial fast cleavage can take place at linkages between residues 9 and 10, 10 and 11, and 12 and 13; more slowly cleaved linkages are between residues 3 and 4, and 8 and 9. Hydrolysis of the B chain by the α-enzyme at pH 9 is still faster and slows down when the chain has been cleaved twice. One fast cleavage is at the linkage between residues 18 and 19; the other can take place at the linkages between residues 12 and 13, and 14 and 15; more slowly cleaved linkages are between residues 8 and 9, 9 and 10, and 15 and 16. Under the conditions tested, the β-enzyme does not hydrolyze the A chain appreciably at pH 9. It cleaves the B chain rapidly at the linkage between residues 23 and 24 and more slowly at linkages between residues 18 and 19. The linkages split by both enzymes are those which involve the carboxyl group of a neutral amino acid.