Define Functions of Manganese?
Like other micro minerals, Mn also functions in mammalian enzyme systems. It can function both as an integral part of metalloenzymes and as an enzyme activator. Manganese containing metalloenzymes are few, as shown in Table, whereas enzymes activated by Mn are much larger in number. Most of these metal activations by Mn are non-specific, as magnesium (Mg) can substitute for Mn. There are a few exceptions where Mn be specifically needed for activation. Examples include, activation of glycosyl transferases, phosphoenol/phruvate carboxykinase and glutarnine synthetase.
Glutamine synthetase found in high concentration in the brain catalyzes the following reaction:
NH3 + Glutamate + ATP + Glutamine + ADP + Pi
Thus, glutamate synthetase converts potentially toxic ammonia into glutamine and helps in the removal of ammonia (NH3) as it is generated. It is interesting to note that even in severe Mn deficiency in animals, brain glutamine synthetase activity is maintained normal, suggesting that this enzyme has a high priority among the enzymes activated by Mn or that Mg can replace Mn.