This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ek, P. Articles by Ronquist, G. Search for Related Content PubMed PubMed Citation Articles by Ek, P. Articles by Ronquist, G.

Exogenous Protein Kinases A and C, But Not Endogenous Prostasome-Associated Protein Kinase, Phosphorylate Semenogelins I and II From Human Semen

JOHAN MALM

HANS LILJA

LENA CARLSSON

GUNNAR RONQUIST

From the ^* Department of Medical Biochemistry and Microbiology, University of Uppsala; Department of Clinical Chemistry, Lund University, University Hospital Malmö; and Department of Clinical Chemistry, University Hospital Uppsala, Sweden.

Correspondence to: Dr Pia Ek, Department of Medical Biochemistry and Microbiology, Box 582, University of Uppsala (e-mail: pia.ek{at}imbim.uu.se).

Semenogelins I and II are the quantitatively dominating proteins in human semen. They comprise the major part of the sperm-entrapping gel formed at ejaculation, which subsequently liquefies due to proteolysis of the gel-forming proteins by prostate-specific antigen (PSA). The mechanism behind gel formation and its physiological significance is not known. We have studied phosphorylation and dephosphorylation of human semenogelins. Both were phosphorylated by protein kinases A and C (PKA and PKC, respectively) at a rate about 5 times less than that of histone. For PKA, incorporated (³²P)phosphate into semenogelin approached a maximum above 1 mol/mol. Corresponding values for phosphorylation of the semenogelins with PKC were greater than 10. There was no change in the sensitivity of phosphosemenogelins to proteolysis by PSA. Serine (PKA) and serine and threonine (PKC) were the phosphate-accepting amino acid residues, and all incorporated (³²P)phosphate could be removed from the semenogelins with human acid phosphatase. Nil or very little phosphate could be detected in purified semenogelins isolated from seminal plasma. In vivo, about half the protein kinase activity in seminal plasma was bound to prostasomes. PKA but not PKC purified from prostasomes could phosphorylate specific substrates, but they could phosphorylate either of the semenogelins.

     Key words: Acid phosphatase, histone, prostate-specific antigen, vasectomy