The chymotrypsin‐like activity of human prostate‐specific antigen, γ‐seminoprotein

Abstract
γ‐Seminoprotein (γ‐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 γ‐Sm was defined as a chymotypsin‐like activity using reduced and S‐3‐(trimethylated amino)propylated lysozyme and insulin‐oxidized A and B chains as substrates. The ‐LeuSer‐ peptide bond of lysozyme was rapidly hydrolyzed by γ‐Sm. γ‐Sm also hydrolyzed the ‐PheGlu‐ of lysozyme and the ‐LeuCys(SO3H) ‐of insulin B chain. Insulin A chain and arginyl‐ or lysyl‐linkage of these proteins were not hydrolyzed by γ‐Sm at all.