[Effect of cAMP on hexokinase and glucose-6-phosphate dehydrogenase isoenzymes in different white rat tissues]

Preincubation of liver and skeletal muscle cytosol obtained from Wistar rats in the presence of cAMP, ATP and MgCl2 inhibited hexokinase. The decrease in the total enzymatic activity was a consequence of inhibition of types 2 and 3 hexokinase. The activity of type 1 hexokinase was unchanged. Under the similar conditions there was a lowering of the total activity of glucose-6-phosphate dehydrogenase which arose from inhibition of types 1 and 2 of the enzyme. The activity of other glucose-6-phosphate dehydrogenase isozymes remained unchanged. Preincubation of adrenal supernatant with cAMP, ATP and MgCl2 did not alter the activity of both enzymes. This is likely to be due to the absence of the respective cAMP-dependent proteinkinases and to the features of the isozyme spectrum. The results obtained indicate that hexokinase and glucose-6-phosphate dehydrogenase can be attributed to the group of enzymes that are regulated by the "phosphorylation-dephosphorylation" mechanism.