ABSTRACT
Numerous enzymes are either zinc metalloenzymes or zinc-enzyme complexes. However, the relationship between the effects of zinc depletion and altered zinc enzyme activity is tenuous at best. Even those enzymes whose activity has been conclusively demonstrated to be reduced in zinc depleted humans or animals have not so far been related to the clinical symptoms of zinc depletion. Zinc metalloenzymes are catalytically active enzymes which, on isolation and purification, have been found to contain stoichiometric amounts of zinc. The activity of these enzymes is usually specifically dependent on the presence of zinc. The function of zinc in such enzymes is one of maintaining structural integrity or one of participation in the enzyme reaction itself. Often these functions are combined. Enzymes that have multiple subunits are typical of those for which zinc would have the function of maintaining structure. The function of zinc in such enzymes is as a Lewis acid or proton donor.
