Abstract
The chemistry of molybdenum is important because of its involvement in a variety of biological processes. Although present in trace quantities, molybdenum is cru cial for..the activity of at2least five enzymes:3 xanthine oxidase,4 aldehyde oxidase, nitrate reductase, sulphite oxidase, and nitrogenase.5 All of these enzymes catalyze redox-type chemical reactions which involve the transfer of two or more electrons per substrate molecule. Electron paramagnetic resonance (EPR) studies1–3,6–8 indicate that, in all but nitrogenase, the molybdenum undergoes oxidation state changes during the catalytic process. Also, the resting state of these enzymes appears to have molybdenum in the +6 oxidation state and molybdenum oxidation state changes are observed only when reducing agents are added to the enzyme.1 All of the enzymes contain two atoms of molybdenum, and in the cases of xanthine oxidase, aldehyde oxidase. and nitrate reductase, two molecules of flavin as well.4 Some researchers believe9 that molybdenum alternates between the +6 and +5 oxidation states during enzyme activity. However, there is evidence10 that the +4 oxidation state also may be involved.
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