Separation of L-cystinyl-di-β-naphthylamide hydrolase (oxytocinase) isoenzymes of human amniotic fluid by acrylamide gel electrophoresis

Human Aminopeptidases: A Review of the Literature

“…It has been shown that the placenta also contains aminopeptidase A (63) and microsomal alanine aminopeptidase, which is immunologically different from serum cystyl aminopeptidase but identical with kidney alanine aminopeptidase (31,36). Several groups have observed a placental enzyme which shares with cystyl aminopeptidase its insensitivity to methionine, its heat lability and the capacity to hydrolyse cystyl-di-ß-naphthylamide, while it has in common with alanine aminopeptidase its microsomal localization and electrophoretic mobility (52,54,58). It is also present in meconiumcontaminated amniotic fluid and colostrum (52,64).…”

“…Several groups have observed a placental enzyme which shares with cystyl aminopeptidase its insensitivity to methionine, its heat lability and the capacity to hydrolyse cystyl-di-ß-naphthylamide, while it has in common with alanine aminopeptidase its microsomal localization and electrophoretic mobility (52,54,58). It is also present in meconiumcontaminated amniotic fluid and colostrum (52,64). A possible explanation for these findings would be some hydrolysis of cystine substrates by microsomal alanine aminopeptidase (65), but the enzyme activity was not found in normal or pregnancy serum.…”

Comparison of Substrates for Measuring Cystyl-Amino Peptidase. Activity in Serum of Pregnancy and Hepatic Disease and in Various Tissues

“…For the assay of cystyl-amino peptidase activity in serum or plasma, cystineamides such as L-cystine-di-j3-naphthylamide (33)(34)(35)(36)(37)(38) and L-cystine-bis-p-nitroanilide (39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49) have been used as substrate. Cysteineamides, e.g.…”