Tissue kallikrein of human seminal plasma is secreted by the prostate gland.

Samples of human seminal plasma were subjected to gel filtration, and the eluted fractions were analysed for their contents of tissue kallikrein-like antigen, arginine esterase activity and kininogenase activity. Two peaks of tissue kallikrein-like antigen were detected with apparent molecular masses of about 72 and 48 kDa. As judged by the criteria of molecular mass, immunoreactivity, kininogenase activity, identification of the released kinin as kallidin and inhibition studies, a genuine tissue kallikrein has been identified in the 48-kDa peak. In addition, this peak contains one or more species of immunoreactive tissue kallikrein which differ in molecular mass and enzymatic activities. The 72-kDa peak probably represents the complex of tissue kallikrein with alpha 1-proteinase inhibitor rather than a true high molecular mass tissue kallikrein. The prostate gland was identified as the site of origin of the tissue kallikrein in the seminal fluid by indirect methods and by demonstrating immunoreactive tissue kallikrein in prostatic tissue and secretion.