魚筋肉プロテアーゼの研究-VI : コイ筋肉カテプシンAおよびDの分離とカテプシンAのいくらかの性質

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Carp muscle cathepsins A and D were separated and partially purified by acid treatment of 0.5% KCI muscle extract, ammonium sulfate fractionation, Sephadex G-200 gel filtration and acetone fractionation. The approximate molecular weight of carp muscle cathepsin A was 34, 000 when determined by dodecyl sulfate-polyacrylamide gel electrophoresis. The pH optima of carp muscle cathepsin A for Cbz-Glu-Phe, Cbz-Glu-Tyr and Cbz-Gly-Phe were near 5.0 and the Km values for these substrates were 3.4, 7.7 and 13.0mM, respectively. Hemoglobin and carp muscle actomyosin were not hydrolyzed by the enzyme preparation while sarcoplasmic protein was hydrolyzed. Carp muscle cathepsin A acted synergistically with cathepsin D in the hydrolysis of hemoglobin. Carp muscle cathepsin A was activated by 2-mercaptoethanol (10-2M), CoCl2, NaBr and NaI (10-3M) while HgCl2 (10-5M), EDTA (10-5M) and iodoacetic acid (10-2M) had no effect. HgCl2 (10-4M), AgNO3 (10-5M) and DFP (10-3M) inhibited the activity considerably.
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