Increased purine nucleotide cycle activity associated with dietary zinc deficiency

Rat muscle 5′-AMP aminohydrolase (EC 3.5.4.6), adenylosuccinate synthetase (EC 6.3.4.4), and adenylosuccinate lyase (EC 4.3.2.2) activities were elevated 50–60% in zinc-deficient weanling rats when compared with restricted-fed zinc supplemental control rats. In addition, the activities of these enzymes were increased by 50–100% when zinc-deficient rats were compared with $\text{ad libitum}$-fed controls. There was no significant difference in total muscle protein or total muscle zinc among the three groups of animals. This increased activity of the purine nucleotide cycle may be responsible for the recently observed increase in blood ammonia in zinc-deficient rats when compared to controls.