Some Properties of Leucine Aminopeptidase from Aspergillus japonica as a Metalloenzyme

概要

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Some properties of purified leucine aminopeptidase [E.C. 3.4.1.1] from Aspergillus japonica as a metalloenzyme were investigated. Leucine aminopeptidase was inhibited by various chelating agents. The addition of Zn^<2+> to the ethylenediaminetetraacetic acid (EDTA)-treated leucine aminopeptidase restored the activity to nearly the original level, but Co^<2+> was partially effective. Kinetic studies using L-leucyl-β-naphthylamide as substrate were carried out with native leucine aminopeptidase, Zn^<2+> or Co^<2+>-reactivated leucine aminopeptidase after dialysis against EDTA. Michaelis constant (K_m) and activation energy (E_<act>) of native leucine aminopeptidase were in good agreement with those of Zn^<2+> reactivated leucine aminopeptidase (native leucine aminopeptidase K_m : 2.5×10^<-4> M, E_<act> : 9.2×10^3 cal/mol, Zn^<2+>-reactivated leucine aminopeptidase K_m : 2.5×10^<-4> M, E_<act> : 9.8×10^3 cal/mol). In the presence of L-leucyl-β-naphthylamide, the inhibition of leucine aminopeptidase by various chelating agents and a Cd^<2+> decreased to an extent of 23-46%. Metal analysis indicated that the purified leucine aminopeptidase containing 1 g-atom of zinc per mol of leucine aminopeptidase, and both the activity and the zinc content were lowered when native leucine aminopeptidase was treated with EDTA or o-phenanthroline.
公益社団法人日本薬学会の論文
1978-10-25