Prostate specific antigen

Prostate specific antigen (PSA) is a single-chain glycoprotein produced by the endoplasmic vesicles of prostate epithelial cells and containing 237 amino acid residues. It has a molecular weight of approximately 34 kD and is functionally a kallikrein-like enzyme. A serine protease. PSA exists in the prostate endoplasmic reticulum and prostate epithelial cells and secretions. PSA is contained in both normal and diseased prostate tissue, and the PSA content of a single cell is relatively constant. 2-Macroglobulin binds and is inactivated, usually without or with very little PSA in the blood.