β-アミラーゼのアスコルビン酸に依る阻害に関する研究 : (第1報)銅イオンの影響

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The inhibitory effect of ascorbic acid on purified β-amylase extracted from sweet potato was studied. (1) In the presence of Cu++, the mechanism of this inhibition is not so simple but rather complex as it is seen in figures 4 to 7. It consists at least of two parts. The one, which prevails in early stage, is reversible and the other, which prevails in later stage, is an irreversible inactivation. (2) The degree of inhibition in early stage has extremely intimate relationship with the rate of autoxidation of ascorbic acid and is the function of the concentration of both Cu++ and ascorbic acid, the former being limiting. These facts suggest that this, inhibition is due to Cu+ formed. The inhibition is reversed even in the course of enzyme reaction. (Fig. 2 and Fig. 7). (3) The part of irreversible inactivation meutioned above seems to occur slowly and integratively from the beginAing of the inhibition and to come from the autoxidation product of ascorbic acid in the presence of Cu++ as a catalyst. This inactivation may be due to H2O2 accumlated. The feeble inactivation by ascorbic acid alone is of the same nature. (4) Minute quantity of Cu++ used inn this experiment causes only several per cent depression of activity in several hours but the activity there after remains unchanged. Preincubation period of enzyme and Cu++ has no effect on the degree of inhibition. (Fig. 3) Hence, once the enzyme preparation is contaminated with traces of Cu++, increased inhibition is caused by ascorbic acid.
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β-アミラーゼのアスコルビン酸に依る阻害に関する研究 : (第1報)銅イオンの影響

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