Figure 5.

Comparison of the enzymatically active prostate-specific antigen (PSA) in tissues and seminal plasma with the inactive forms of free PSA found in serum: Active PSA contains no internal peptide bond cleavages and forms a complex with α₁-antichymotrypsin (PSA-ACT) in serum. proPSA is a precursor form of PSA that is expressed with a 7-amino acid N-terminus leader peptide but is found in serum containing from 1 to 7 amino acids. “Benign” PSA (BPSA) contains 2 internal peptide bond cleavages. The remainder of the inactive PSA in serum (iPSA) appears to be composed largely of intact, denatured PSA, although it may contain lesser amounts of internal or N-terminus cleavages. BPH, benign prostatic hyperplasia. Adapted, with permission, from Mikolajczyk SD et al. Urology. 2002;59:797–802.⁸⁷