PSA (prostate-specific antigen) is a serine protease of the kallikrein family. Its biological function in semen is to:

• A Act as the primary protease for sperm capacitation
• B Stimulate prostatic epithelial cell proliferation by autocrine signalling
• C Cleave semenogelin proteins to liquify semen after ejaculation ✓
• D Inhibit prostatic fibrinolysis by inactivating urokinase plasminogen activator

Explanation

PSA (also called kallikrein-3, KLK3) is a serine protease secreted by prostatic epithelial cells. Its physiological role is to cleave semenogelin I, semenogelin II and fibronectin, proteins of the seminal vesicle coagulum that form immediately after ejaculation. PSA-mediated proteolysis liquefies the semen gel within 20–30 minutes, releasing sperm for motility. PSA does not directly capacitate sperm or stimulate prostatic proliferation. It does not inhibit fibrinolysis. In plasma, PSA is predominantly bound to alpha-1-antichymotrypsin and alpha-2-macroglobulin; free PSA fraction is used clinically to improve specificity in PSA grey zone.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.