Zinc is a cofactor for

More than 300 enzymes are zinc-dependent. Some impoant ones are carboxypeptidase, carbonic anhydrase, alkaline phosphatase, lactate dehydrogenase, alcoholdehydrogenase and glutamate dehydrogenase. RNA polymerase contains zinc and so it is required for protein biosynthesis. Extracellular superoxide dismutase is zinc-dependentand so, zinc has antioxidant activity.Alternatively, all-trans-retinal is transpoed to liver and then reduced to all-trans-retinol by alcohol dehydrogenase (ADH), an NADH dependent enzyme. ADH contains zinc, and therefore, zinc is impoant in retinol metabolism. The all-trans-retinol is isomerized to 11-cis-retinol and then oxidized to 11-cis-retinal in the liver. This is then transpoed to the retina. This completes the Wald&;s visual cycleRef: DM Vasudevan, Page no: 429