Purification and properties of leucine aminopeptidase from Aspegillus japonica. II.

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Abstract
Leucine aminopeptidase was purified from culture filtrate of A. japonicus by calcium acetate treatment, ammonium sulfate fractionation, and column chromatography with DEAE-cellulose, Sephadex G-100 and CM[carboxymethyl]-Sephadex C-50. The purified enzyme was homogeneous in disc electrophoretic analysis. Its MW was estimated to be 57,000 by Sephadex G-75 gel-filtration. The enzyme was most active at pH 8.0 toward L-leucylglycylglycine (Leu-Gly-Gly) and L-leucyl .beta.-naphthylamide (Leu-.beta.-NA), and its optimum temperature was 50.degree. C. The enzyme was stable in a pH range of 5.5-8.5 and below 50.degree. C. The purified enzyme was highly activated by Co2+ and was strongly inhibited by Fe3+, Hg2+, Cu2+, Pb2+, Ni2+, EDTA, o-phenanthroline and N-bromosuccinimide. It was not affected by SH-reagents and diisopropyl fluorophosphate (DFP). The enzyme is considered to be leucine aminopeptidase, because it preferentially hydrolyzed di- or tripeptides with N-terminal leucine.

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