{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Prostate-specific antigen (PSA) is an androgen-regulated serine protease produced by both prostate epithelial cells and prostate cancer cells. PSA is a major protein in semen, where its function is to cleave semenogelins in the seminal coagulum. PSA is secreted into prostatic ducts as an inactive 244-amino acid proenzyme (proPSA) that is activated by cleavage of seven N-terminal amino acids. PSA is also present in small quantities in the serum of normal men, and is often elevated in the presence of prostate cancer and in other prostate disorders. According to literature, most prostatic carcinomas express PSA."}]}]}