Abstract

In several recent publications (14) it has been reported that dietary aminopterin produces a marked decrease in rat liver choline oxidase activity as measured by the whole homogenate technique. A simple folic acid deficiency, however, has been shown to produce only slight changes in the activity of this enzyme (5). It was probable that a simple folic acid deficiency did not deplete the tissues of folic (and folinic) acid to a great enough extent to produce much change in the activity of the whole homogenate. If only minute amounts of a folic acid cofactor were needed by the enzyme, a whole liver homogenate, even from deficient animals, might contain enough of the cofactor to maintain the normal activity of the enzyme. The choline oxidase system of rat liver has been shown to be located in the mitochondrial fraction of liver (6-S). Therefore, the authors felt that, if the mitochondria were isolated, washed, and thus freed of extraneous folic acid, folinic acid, or cofactor containing either of these in bound form, the effects of a simple folic acid deficiency could be demonstrated more clearly. In the present investigation not only the effect of a simple folic acid deficiency on the choline oxidase of isolated mitochondria has been studied, but also a comparison has been made with the effects on the mitochondrial activity of the enzyme produced by feeding aminopterin to rats. In order to complement the enzyme results, and to study the correlation of the eneyme activity with folic acid and folinic acid’ concentration in the tissues, all of the samples used for the enzyme determinations were assayed microbiologically for both folic acid and folinic acid. In the course of these

Highlights

  • The results indicate that the choline oxidase in folic acid-deficient mitochondria is less active than that in normal mitochondria

  • The relation of the substrate concentration to this effect in the mitochondrial system has been found to be very important in interpreting enzyme data in which the normal and the abnormal systems are compared

  • Analyses of the whole liver and liver mitochondria of normal and folic acid-deficient rats for folic and folinic acids indicate that these substances are markedly decreased in a folic acid deficiency

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Summary

OF THE DEPOSITION OF FOLIC AND TO CHOLINE OXIDASE OF ISOLATED

A simple folic acid deficiency, has been shown to produce only slight changes in the activity of this enzyme (5). It was probable that a simple folic acid deficiency did not deplete the tissues of folic (and folinic) acid to a great enough extent to produce much change in the activity of the whole homogenate. In the present investigation the effect of a simple folic acid deficiency on the choline oxidase of isolated mitochondria has been studied, and a comparison has been made with the effects on the mitochondrial activity of the enzyme produced by feeding aminopterin to rats. $ Postdoctorate fellow of The China Foundation for the Promotion of Education and Culture.

ACID AND CHOLINE
Volume of system
PER FLASK
Folic acid
Findings
SUMMARY
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