Manganese is a component of the antioxidant enzyme superoxide dismutase (SOD), which is present in all aerobic cells, where it is required for the de-toxification of oxygen metabolites. Manganese is also a cofactor for the enzymes hexokinase, pyruvate carboxylase, PEP carboxylase, glutamine synthetase, and xanthine oxidase (among others). It is required for the action of vitamin B1 (thiamine) and for normal brain function (due to its role as an activator of brain enzymes); manganese deficiency can be associated with epilepsy [4,5]. Mn is also required for bone and cartilage formation; low levels are often associated with
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joint surface diseases, e.g. arthritis [6,7]. Manganese has a hypoglycaemic activity by virtue of its effect on gluconeogenesis and low manganese concentrations may be found in diabetes mellitus. In the thyroid gland, Mn2+ stimulates conversion of MIT (mono-iodotyrosine) to DIT (diiodo-tyrosine) during thyroid hormone synthesis.