Editing Prostate-specific antigen (section)

==Mechanism of action==

The physiological function of KLK3 is the dissolution of the coagulum, the sperm-entrapping gel composed of [[semenogelin]]s and [[fibronectin]]. Its proteolytic action is effective in liquefying the coagulum so that the sperm can be liberated. The activity of PSA is well regulated. In the prostate, it is present as an inactive pro-form, which is activated through the action of [[KLK2]], another kallikrein-related peptidase. In the prostate, zinc ion concentrations are 10 times higher than in other bodily fluids. Zinc ions have a strong inhibitory effect on the activity of PSA and on that of KLK2, so that PSA is totally inactive.<ref>{{cite journal | vauthors = Hara M, Kimura H | title = Two prostate-specific antigens, gamma-seminoprotein and beta-microseminoprotein | journal = The Journal of Laboratory and Clinical Medicine | volume = 113 | issue = 5 | pages = 541–548 | date = May 1989 | pmid = 2654306 | url = https://www.translationalres.com/article/0022-2143(89)90023-1/fulltext#%20 }}</ref>

Further regulation is achieved through pH variations. Although its activity is increased by higher pH, the inhibitory effect of zinc also increases. The pH of semen is slightly alkaline and the concentrations of zinc are high. On ejaculation, semen is exposed to the acidic pH of the [[vagina]], due to the presence of [[lactic acid]]. In fertile couples, the final vaginal pH after coitus approaches the 6-7 levels, which coincides well with reduced zinc inhibition of PSA. At these pH levels, the reduced PSA activity is countered by a decrease in zinc inhibition. Thus, the coagulum is slowly liquefied, releasing the sperm in a well-regulated manner.{{citation needed|date=May 2021}}