Oxytocinase-like enzyme in an ovarian dysgerminoma: A placenta-specific protein

Aminopeptidase from dysgerminoma was purified and characterized using l-leucine-β-naphthylamide as substrate. The enzyme was resistant to puromycine, methionine, amastatin, bastatin, and EDTA, and it was heat labile at 60°C. The enzyme showed the same electrophoretic mobility as pregnant-patient serum oxytocinase CAP₁ on polyacrylamide gel electrophoresis. K_m value against S-benzylcysteine-p-nitroanilide was 4.2 × 10⁻⁴m. Oxytocin and vasopressin competitively inhibited the enzyme activity. Molecular weight of the enzyme was estimated to be 80,000 by Sephadex G-200 column chromatography. These results suggest that aminopeptidase from dysgerminoma is an oxytocinase-like enzyme, a placenta-specific protein.