Lyophyllum cinerascens aminopeptidase: purification and enzymatic properties.
An aminopeptidase (EC 3.4.11.1) was purified from the extract of Lyophyllum cinerascens by ammonium sulfate fractionation and sequential chromatographies on DEAE-Sephadex, Sephadex G-150, HPLC-phenyl-5PW, and HPLC-DEAE-5PW columns, with an activity recovery of 4.6% using Leu-beta-naphthylamide as a substrate. The enzyme was a tetrameric protein of molecular weight 150,000 and was found to be rich in histidine. It exhibited a pH optimum of 7.2 and stability between pH 5.7 and 7.7. The isoelectric point of the enzyme was 4.6. The enzyme catalyzed the hydrolysis of amino acid beta-naphthylamides, Phe greater than Leu greater than Met greater than Tyr greater than Ala greater than Glu, and the differences of the measured kcat's ranged over 2-3 orders of magnitude while many of the amino acid beta-naphthylamides were not hydrolyzed at all. Other interesting comparisons include two aliphatics, Ala vs Leu, and the aromatics, Tyr vs Phe, which show a 30-fold difference in the kcat/Km values. The enzyme also hydrolyzed Leu-Gly-Gly and the B chain of oxidized insulin to release N-terminal leucine and phenylalanine, respectively. The release of N-terminal Phe from the oxidized B chain is interesting in view of the fact that the penultimate residue is Val, an unfavorable amino acid in the beta-naphthylamide series. The enzyme seems to be a true aminopeptidase, requiring the free amino groups and hydrolyzing dipeptide and oligopeptide from the N-terminal end. The enzyme was resistant to the action of amastatin. Neither sulfhydryl reagents nor serine protease inhibitors affected the enzyme activity; however, the enzyme was inhibited weakly by EDTA and bestatin and strongly by diethyl pyrocarbonate.
School of Pharmaceutical Sciences, Nagasaki University, Japan.
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AK
Abdus Sattar
T
T
Yoshimoto
D
D
Tsuru
D000363:Agaricales / Q000201:enzymology*; D000626:Aminopeptidases / Q000302:isolation & purification* / Q000378:metabolism; D002850:Chromatography, Gel / Q000379:methods; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D002852:Chromatography, Ion Exchange / Q000379:methods; D004795:Enzyme Stability; D007700:Kinetics; D046911:Macromolecular Substances; D008970:Molecular Weight; D013379:Substrate Specificity
D046911:Macromolecular Substances; D000626:Aminopeptidases