Liquefaction of coagulated human semen.

Liquefaction of coagulated human semen was inhibited by o-phenanthroline; subsequent addition of Zn2+ reversed this inhibition, but not if the coagulum was repeatedly washed before Zn2+ was added. No liquefaction of the coagulum occurred when Fe2+ was added (in a 1:3 molar ratio to o-phenanthroline), and the gel repeatedly washed. This o-phenanthroline-depleted coagulum was liquefied by resuspended pellet from ultracentrifuged pooled seminal plasma. In denatured and reduced semen coagulate, we identified the 52 kDa, 71 kDa, and 76 kDa protein bands of the predominant seminal vesicle protein. The protein was not present in the supernatant after centrifugation of coagulated semen, and it was degraded to several minor basic proteins when semen liquefied. These findings imply that the predominant seminal vesicle protein functions as the structural protein of coagulated semen. In much the same way as in ejaculated semen, the 52 kDa, 71 kDa, and 76 kDa protein bands in seminal vesicle secretion collected postmortem were digested to minor basic proteins after incubating the secretion with resuspended pellet from ultracentrifuged seminal plasma. This pellet contained the membrane-bound succinyl(alanine)3-p-nitroanilide hydrolysing peptidase of prostatic origin which, like the liquefaction process, was active in the presence of EGTA, inhibited by non-chelated Zn2+, and inactivated by o-phenanthroline--an inactivation that was reversed by Zn2+.