Two prostate-specific antigens, gamma-seminoprotein and beta-microseminoprotein

Abstract

The determination of gamma-seminoprotein (gamma-Sm) (also called prostate-specific antigen [PSA], prostate antigen [PA], or p30) in human serum has been recently demonstrated to be more sensitive and specific for diagnosing prostate cancer and monitoring the condition of patients with prostate cancer than the prostatic acid phosphatase (PAP) test. Because the gamma-Sm (PSA) test seems likely to replace the PAP test in the area of urology and study of prostate-specific antigens is expanding, we have reviewed physicochemical properties and clinical significance of two prostate-specific antigens, gamma-Sm (PSA) and beta-microseminoprotein (beta-MSP). Both proteins have been proved to originate in the prostate gland and have not been detected in any other human tissues by an immunohistologic study. The usefulness of gamma-Sm and beta-MSP in determining the origin of metastatic tumors has also been shown. gamma-Sm is a glycoprotein with a molecular weight of 26,079 for the peptide portion, of which the amino acid sequence is identical to so-called PSA and homologous with serine proteases (the kallikrein family). Its chymotrypsin-like activity with a unique substrate specificity has also been demonstrated. The molecular weight of beta-MSP is 10,652 from the amino acid sequence, in which the protein has been shown to contain no alanine residue.