パン酵母ピルビン酸デカルボキシラーゼの等電点とpI5.83標品の性状について

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Isoelectric point of pyruvate decarbaxylase from baker's, yeast was determined on both crude extract and partially purified preparation by isoelectric fractionation with Ampholine, a carrier ampholyte. The enzymic activity was distributed mainly at pI 5.6 fraction and weakly at pI 5.9 in case of crude extract. The activity at pI 5.6 fraction, however, disappeared in course of purification. Two kinds of pyruvate decarboxylase were separated by DEAE-cellulose column chromatography ; one of them was lost most of its activity by isoelectric fractionation, leaving trace of activity at pI 6.17 and pI 6.36 fractions, whereas the other was concentrated at pI 5.83 fraction. Though pI 5.83 preparation looked pure, the enzymic activity was lost by repeating isoelectric fractionation, leaving a trace activity at pI 6.1〜6.4 fraction. pI 5.83 preparation did not need Mg ion for its enzymic reaction ; Mg ion exhibited an inhibitory effect. Pyruvate decarboxylase reaction catalyzed by the preparation was analyzed according to Ingraham・Makower equation, a rate equation for two-substrate enzyme reaction, regard ing cocarboxylase as a substrate as well as pyruvate. The kinetic data were explained as follows : Rate of reaction was limited by forming enzyme-cocarboxylase-pyruvate ternary complex. The reaction may proceed through either one of two binary complexes, enzyme-cocarboxylase and enzyme-pyruvate, but mainly through enzyme-cocarboxylase complex. Affinity of cocarboxylase for enzyme-pyruvate complex was much less than that for free enzyme.
日本ビタミン学会の論文
1969-11-25

パン酵母ピルビン酸デカルボキシラーゼの等電点とpI5.83標品の性状について

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