Enzymatic activity of prostate-specific antigen and its reactions with extracellular serine proteinase inhibitors

Eur J Biochem. 1990 Dec 27;194(3):755-63. doi: 10.1111/j.1432-1033.1990.tb19466.x.


Prostate-specific antigen (PSA) is one of the three most abundant prostatic-secreted proteins in human semen. It is a serine proteinase that, in its primary structure, manifests extensive similarities with that of the Arg-restricted glandular kallikrein-like proteinases. When isolated from semen by the addition of chromatography on aprotinin-Sepharose to a previously described procedure, PSA displayed chymotrypsin-like activity and cleaved semenogelin and the semenogelin-related proteins in a rapid and characteristic pattern, but had no trypsin-like activity. About one third of the purified protein was found to be enzymatically inactive, due to cleavage carboxy-terminal of Lys145. Active PSA formed SDS-stable complexes with alpha 1-antichymotrypsin, alpha 2-macroglobulin-analogue pregnancy zone protein. PSA formed inhibitory complexes with alpha 1-antichymotrypsin at a molar ratio of 1:1, a reaction in which PSA cleaved the inhibitor in a position identical to that reported from the reaction between chymotrypsin and alpha 1-antichymotrypsin. The formation of stable complexes between PSA and alpha 1-antichymotrypsin occurred at a much slower rate than that between chymotrypsin and alpha 1-antichymotrypsin, and at a similar or slightly slower rate than that between PSA and alpha 2-macroglobulin. When added to normal blood plasma in vitro, active PSA formed stable complexes both with alpha 2-macroglobulin and alpha 1-antichymotrypsin. This complex formation may be a crucial determinant of the turnover of active PSA in intercellular fluid or blood plasma in vivo.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Antigens, Neoplasm / isolation & purification
  • Antigens, Neoplasm / metabolism*
  • Chromatography, Gel
  • Electrophoresis, Polyacrylamide Gel
  • Humans
  • Hydrolysis
  • Male
  • Molecular Sequence Data
  • Prostate-Specific Antigen
  • Serine Proteinase Inhibitors / metabolism*
  • alpha 1-Antichymotrypsin / metabolism
  • alpha-Macroglobulins / metabolism


  • Antigens, Neoplasm
  • Serine Proteinase Inhibitors
  • alpha 1-Antichymotrypsin
  • alpha-Macroglobulins
  • Prostate-Specific Antigen