Abstract
Summary
Several indirect mechanisms of glucose repression, not involving changes in the in vivo concentration of hepatic adenosine 3′,5′-monophosphate, were explored. Glucose, while repressing the induction of the serine dehydratase and tyrosine aminotransferase, does not interfere with the in vivo glucagon-stimulated, 3′,5′-AMP-mediated transport of α-aminoisobutyric acid in rat liver. No changes were noted in the in vitro binding of 3′,5′-AMP to receptor proteins in cell fractions and in purified preparations from rat liver when glucose or other carbohydrates were added to the reaction mixture. At physiological concentrations, glucose and other carbohydrates did not alter the phosphorylation of histones by hepatic or beef muscle protein kinases. At very high concentrations of several triose and hexose phosphates, only a slight inhibition of protein kinase activity was noted. Complete inhibition, however, was obtained with 25 mM 2,3-diphosphoglyceric acid.
This work was supported in part by Public Health Service Special Research Fellowship 5-F03-GM-35641-04, NIH Grants RR-05410-10 and CA-07175 and American Cancer Society Grants E588 and IN-57-L. We thank Mrs. Anabelle Cutler and Renata Gunter for their able technical assistance, and Dr. Angel Pestaña for his help in the performance of the amino acid transport experiments.
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