The effect of palmityl coenzyme A on glucose 6-phosphate dehydrogenase and other enzymes.

Palmityl coenzyme A was found to inhibit and inactivate both purified yeast and crude rat liver glucose 6-phosphate dehydrogenase. The yeast enzyme was inhibited 50% at a concentration of 0.0031 mm. The inhibition was strictly competitive and reversible with respect to glucose 6-phosphate and of the mixed type with respect to TPN. Bovine serum albumin and hydroxylamine both prevented and reversed the inhibition, but no restoration of activity was possible once the enzyme became inactivated. Of a group of 12 other enzymes of diverse metabolic function which were tested, 7 were inhibited or inactivated, or both, by very low concentrations of the acyl ester. Glutamic dehydrogenase was found to be the most sensitive as 50% inhibition occurred at 3 X 10F4 mM. In view of the widespread inhibition of enzymes by palmityl coenzyme A and other acyl coenzyme A esters, the physiological role of these esters as regulators of certain metabolic pathways must be viewed with reservation.