Human Skeletal Muscle Contains Two Major Aminopeptidases: an Anion-Activated Aminopeptidase B and an Aminopeptidase M-Like Enzyme

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Two major aminopeptidases, an aminopeptidase B and an aminopeptidase M-like enzyme, were purified from human skeletal muscle by DEAE-cellulose, HPLC gel filtration, and hydroxyapatite column chromatographies. The purified aminopep-tidase B exhibits a molecular weight of 76, 000 under both native and denaturing conditions. The activity of the aminopeptidase B is regulated by Cl ions and other anions in vitro. On the other hand, the aminopeptidase M-like enzyme is a mono-meric protein having a molecular weight of 96, 000. It is capable of significantly cleaving Phe-, Leu-, Arg-, and Ala-aminoacyl bonds in the presence of 2-mercapto-ethanol. The pH optima for both enzymes are around 7.0, and bestatin is an effective inhibitor of both enzymes.