Oxytocinase activity in human spermatozoa and its possible role in fertilization.
Human spermatozoa were extracted with 1% Triton X-100 and analyzed for oxytocinase (E.C. 3.4.11.3) activity by means of two synthetic peptides. S-benzyl-L-cysteine-p-nitroanilide (BCN) and L-leucine-p-nitroanilide (LN), separately as substrates. The specific activity (mean +/- SD) of this proteolytic enzyme at Vmax in eight different extracts was 0.150 +/- 0.072 and 1.392 +/- 0.602 mIU/10(6) cells using BCN and LN, respectively. The enzyme showed optimal activity at pH 7.2 when BCN was the substrate, and at pH 7.4 with LN as the substrate. Spermatozoal oxytocinase activity may be involved directly or indirectly in the reproductive mechanisms leading to sperm acrosome reaction and fertilization.
Roy
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Department of Obstetrics and Gynaecology, National University of Singapore, National University Hospital.
Ratnam
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D000328:Adult; D000626:Aminopeptidases / Q000378:metabolism*; D000813:Anilides; D003545:Cysteine / Q000031:analogs & derivatives; D010122:Cystinyl Aminopeptidase / Q000378:metabolism*; D005306:Fertilization; D006801:Humans; D008297:Male; D013094:Spermatozoa / Q000201:enzymology*
D000813:Anilides; C001536:1-leucine-4-nitroanilide; C004559:S-benzyl-L-cysteine-4'-nitroanilide; D000626:Aminopeptidases; D010122:Cystinyl Aminopeptidase; D003545:Cysteine