The chymotrypsin-like activity of human prostate-specific antigen, gamma-seminoprotein

gamma-Seminoprotein (gamma-Sm) is a human prostate-specific antigen and a serine protease judging from the complete amino acid sequence which shows extensive homology with the kallikrein family. The enzymatic activity of gamma-Sm was defined as a chymotrypsin-like activity using reduced and S-3-(trimethylated amino)propylated lysozyme and insulin-oxidized A and B chains as substrates. The -Leu/Ser- peptide bond of lysozyme was rapidly hydrolyzed by gamma-Sm. gamma-Sm also hydrolyzed the -Phe/Glu- of lysozyme and the -Leu/Cys(SO3H)- of insulin B chain. Insulin A chain and arginyl- or lysyl-linkage of these proteins were not hydrolyzed by gamma-Sm at all.