A NOTE ON THE IDENTITY OF PORCINE LIVER CARBOXYLESTERASE AND PROLYL-BETA-NAPHTHYLAMIDASE

Prolyl-beta-naphthylamidase from porcine liver is compared with the tw o prevalent isoenzymes of pig liver carboxylesterase by isoelectrofocu sing experiments and by inhibition studies with phenyl-methyl-sulfonyl fluoride. The results suggest that prolyl-beta-naphthylamidase is ide ntical with the amide-cleaving isoenzyme of carboxylesterase, not with the usually predominant methyl butyrate-hydrolysing isoenzyme. It is questionable whether the recently published sequence of prolyl-beta-na phthylamidase does belong to this enzyme or to the predominant carboxy lesterase without amidase activity. Surprisingly, the amide-cleaving c arboxylesterase isoenzymes from rat liver have almost no activity with prolyl-beta-naphthylamide.