Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C1519176 (PSA)
 5,490 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human prostate specific antigen, PSA, is a product of the human glandular kallikrein gene locus on chromosome 19 that is almost selectively expressed by prostate tissue. PSA is one of the dominating prostate derived proteins in seminal fluid. The mature form of PSA, a single chain glycoprotein of 237 amino acids, is a serine protease manifesting restricted chymotrypsin-like activity. PSA is mainly responsible for gel dissolution in freshly ejaculated semen by proteolysis of the major gel forming proteins, semenogelin I and II, and fibronectin. In semen approximately two thirds of PSA is enzymatically active. The remaining 30-40% is inactive due to internal cleavage(s). A few per cent of PSA in semen is complexed to the protein C inhibitor. PSA complexed to alpha 1-antichymotrypsin (ACT) constitutes the predominant molecular form of serum PSA, although complex formation is slow between the purified proteins in vitro. PSA also forms stable complexes with alpha 2-macroglobulin in vitro but as this results in encapsulation of PSA and complete loss of the PSA-epitopes, the in vivo significance of this complex formation is presently unclear. A free, non-complexed form of PSA constitutes a minor fraction of the serum PSA despite the large molar excess of antiproteasees such as ACT. In patients with carcinoma of the prostate the serum PSA level increases. Analysis of the serum level of PSA is used both for diagnosing and monitoring patients with carcinoma of the prostate (CAP).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Biochemistry of prostate specific antigen, PSA. 754 81

We have recently demonstrated in liquefied human seminal plasma the presence of the novel kallikrein hK2 in association with protein C inhibitor (PCI) as a 75-kDa complex. In the present study, we showed that hK2, immediately after ejaculation, was recovered only in its free form but complex formation with PCI occurred rapidly thereafter and was completed within 10 minutes. That reaction required an enzymatically active kallikrein. In order to determine the patterns of hydrolysis of major seminal vesicle proteins, semenogelins and fibronectin were exposed to hK2 and to hK3 (prostate-specific antigen or PSA) and cleavage sequences were identified by N-terminal sequencing. Free hK2 was able to hydrolyze semenogelins and fibronectin in vitro. Most of cleavage sites were at the carboxyl-side of arginyl residues. Semenogelins were hydrolyzed to a similar extent by catalytic (and similar) concentration of either hK2 or PSA though no common cleavage sites was identified for both proteinases. Unlike semenogelins, fibronectin was hydrolyzed much more efficiently by hK2 than by PSA. These results show that hK2 is enzymatically active during a short period of time after ejaculation, that major seminal vesicle proteins can be the target of this proteolytic activity, and that hK2 and PSA have different substrate specificities.
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PMID:Potential involvement of kallikrein hK2 in the hydrolysis of the human seminal vesicle proteins after ejaculation. 901 96