Acidic Cysteine Proteinase Inhibitor in Seminal Plasma

Abstract
A cysteine proteinase inhibitor with acidic isoelectric point (pI = 4.7-5.0) was found in human seminal plasma. Its apparent MW is 16 kDa. It inhibits cysteine proteinases like ficin, cathepsin H, cathepsin B and papain. The inhibitory activity of seminal plasma against ficin is almost the same as that of human serum.