Fractionation and characterization of oxytocinases in human semen

Abstract

Summary. Two isoenzymes of oxytocinase activity were fractionated from human seminal plasma by acrylamide\p=n-\agarosegel chromatography and partly characterized using S-benzyl-L-cysteine-p-nitroanilide (BCN) and L-leucine-p-nitroanilide (LN) separately as substrates. These isoenzymes appeared to be metallo-aminopeptidases with different elution volumes (90 ml and 150 ml), apparent molecular weights (unknown value and 300 000) and pH optima (6\m=.\8and 7\m=.\0with BCN and 7\m=.\2and 7\ m=. \ 4 with LN), but with similar substrate affinity and thermal sensitivity, and susceptibility to EDTA, divalent metal ions, L-methionine, polypeptide hormones and prostaglandins. A comparison of the enzymic properties with pregnancy-associated oxytocinases suggests that seminal oxytocinases are related more closely to amniotic fluid isoenzymes than to pregnancy serum, placental and uterine isoenzymes.

A Neuropeptide in Human Semen: Oxytocin

“…This, together with the fact that the concentrations of seminal OT were not measured, make a comparison to our study difficult. Finally, human seminal plasma contains huge amounts of oxytocinases [16], which makes it even more difficult to draw conclusions. Although the activity of oxytocinases is supposed to play a role in fertilization [ 151, a clear dose-dependent relationship of these enzymes has neither been found with semen plasma OT levels nor with spermatozoa characteristics.…”