Adverse Effects of Zinc Deficiency: A Review from the Literature

tial element for more than a hundred years, ever since it was discovered by Raulin in 1869 to be required for the growth of Aspergillus niger. However, it has not been until relatively modern times that the universal importance of this metal for both human and animal health became fully appreciated. To date more than 200 zinc dependent enzymes have actually been identified in all the main biochemical pathways. It acts uniquely as a Lewis acid catalyst (an electron acceptor) in all life processes. The metal is known to be essential for the function and/or structure of several dehydrogenases, aldolases, peptidases, phosphatases, an isomerase, a transphosphorylase, aspartate transcarbamylase, pancreatic carboxpeptidase, and tryptophan desmolase. Zinc-dependent metalloenzymes are also found among oxidoreductases, transferases, hydrolases, lyases, isomerases and ligases. Zinc is also required for the action of both carbonic anhydrase and superoxide dismutase. The metal has also been found to be an essential component of both DNA and RNA polymerases. 22 It is also vital for a variety of hormonal activities, including the thymic hormone, glucagon, insulin, growth hormone, as well as the sex hormones. Furthermore, zinc has been found to be essential for normal brain development, particularly concerning the hippocampal function. In addition, zinc is also known for its antiviral, antibacterial, antifungal, and anticancer properties, and has been found to protect animals against otherwise lethal irradiation by neutrons.