Prostate specific antigen (PSA) is a single chain glycoprotein containing two
hundred forty amino acid residues and four carbohydrate side chains. The
complete gene encoding PSA has been sequenced and localized to chromosome 19. 1
PSA functions as a kallikrein-like serine protease and is produced exclusively
by the epithelial cells lining the acini and ducts of the prostate gland. 2-4
It is secreted into the prostatic ducts, and at ejaculation it serves to
liquefy the seminal coagulum. 5 The detection of PSA by enzyme-linked
immunosorbent assay (ELISA) has been demonstrated. The range of normal serum
PSA concentration is 0.1 to 2.6 ng/ml, and the half life of serum PSA has been
determined to be 2.2 to 3.2 days. 7-8 Many studies have confirmed that PSA is
the most useful and meaningful tumor marker known for prostate cancer.
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