ENZYMIC ADAPTATION RELATED TO CARBOHYDRATE METABOLISM IN ANIMAL BODY.
Final rept. 15 June 62-14 June 63,
TOKYO BIOCHEMICAL RESEARCH FOUNDATION (JAPAN)
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The activities of the enzymes of carbohydrate metabolism are changed in animal body when the animal is fed with a high carbohydrate diet after fasting. This phenomenon could be interpreted as an adaptation mechanism. Especially, the changes in the enzymic activities of the pentose phosphate pathway would affect the production of NADPH which would be related to lipid synthesis from carbohydrate. In the present studies the rats were fed with a high carbohydrate diet after fasting, and the activities of the enzymes related to the pentose phosphate pathway were determined. The rate-limiting step of the pentose phosphate pathway was concluded to be the activity of this enzyme and the ratio of NADPNADPH. When the enzyme was purified from rat liver, there was no essential difference of the enzyme between fasted rats and refed rats. There was no difference in the kinetic properties and the stability of the enzyme, either. It is not probable that the enzyme activator or inhibitor plays an important role in this adaptation phenomenon, and the most probable cause could be concluded to be the change in the quantity of the enzyme. The supporting evidence was obtained from the fact that this adaptation is lost by the administration of 8-azaquanine to the rats. Author