Vanadium biological function

Vanadium a versatile biochemical effector with an elusive biological function. D. W. Boyd and K. Kustin, Adv. Inorg. Biochem., 1984, 6, 311 (291). 

Sjbberg B-M (1997) Ribonucleotide Reductases - A Group of Enzymes with Different Metallosites and a Similar Reaction Mechanism. 88 139-174 Slebodnick C, Hamstra BJ, Pecoraro VL (1997) Modeling the Biological Chemistry of Vanadium Structural and Reactivity Studies Elucidating Biological Function. 89 51-108 Smit HHA, see Thiel RC (1993) 81 1-40... 

Each of these minerals participate in a variety of biologic functions and is necessary for normal metabolism. Other trace minerals essential to humans but for which deficiency states have not been recognized include nickel, vanadium, cobalt, and silicon (Table 66.2). 

The potentially serious aspects of vanadium pollution, the function of biologically occurring enzyme systems, the role of vanadium on the function of numerous enzymes, and the associated role in the insulin-mimetic vanadium compounds are inextricably linked. The key to our understanding all such functionality relies on understanding the basic chemistry that underlies it. This chemistry is determined to a significant extent by the V(IV) and V(V) oxidation states but clearly is not restricted to these states. Indeed, the redox interplay between the vanadium oxidation states can be a critical aspect of the biological functionality of vanadium, particularly in enzymes such as the vanadium-dependent nitrogenases, where redox reactions are the basis of the enzyme functionality. 

Molybdenum is very important in the biochemistry of animals, plants, and microorganisms. It is the only element in the second transition series known to have natural biological functions. It occurs in more than 30 enzymes, in some of which it may be replaced by tungsten or vanadium. Tungsten is the only element in the third transition series known to have natural biological functions. Not only does it sometimes occur in enzymes that usually contain molybdenum, but there are some enzymes that are known only with tungsten. 

Storage and transport of vanadium are specialized affairs. Just why certain organisms accumulate high levels of vanadium is unknown and the biological functions of this trace metal have yet to be established. 

Thus, the findings to date suggest that vanadium has a biological function in controlling one or more enzymatic reactions concerned with phosphate metabolism. However, further in vivo studies are necessary before a conclusive statement can be made. 

Medical Significance. The medical significance of vanadium is unclear because knowledge is incomplete of the conditions necessary to produce vanadium deficiency, dietary components that affect vanadlinn metabolism, and its biological function. 

Vanadium, like molybdenum, has two very different catalytic activities associated with it and two very different biological functions. Both elements... 

Many of the most important catalytic activities of coordination compounds and metal ions (particularly iron and copper) are in the electron transport chains of cellular metabolism, where they act as catalysts for the oxidation of organic intermediates. Several other transition metal ions (including vanadium and molybdenum) have important metabolic roles in a variety of organisms. Indeed, recent discoveries suggest that even such metals as chromium and nickel have biological functions. 

As yet, the biological functions of vanadium have not been defined clearly. However, vanadium has an effect on the activity of important enzymes, especially the inhibition of (Na,K)-ATPase, other ATPases, phosphatases and phosphotransferases by metavanadate ions (VO ). Vanadium also stimulates the synthesis of cychc AMP by adenylate cyclase activation and may therefore interfere with the metabolism of carbohydrates and lipids. 

The quality of the experimental evidence for nutritional essentiality varies widely for the ultratrace elements. The evidence for the essentiality of three elements, iodine, molybdenum and selenium, is substantial and noncontroversial specific biochemical functions have been defined for these elements. The nutritional importance of iodine and selenium are such that they have separate entries in this encyclopedia. Molybdenum, however, is given very little nutritional attention, apparently because a deficiency of this element has not been unequivocally identified in humans other than individuals nourished by total parenteral nutrition or with genetic defects causing disturbances in metabolic pathways involving this element. Specific biochemical functions have not been defined for the other 15 ultratrace elements listed above. Thus, their essentiality is based on circumstantial evidence, which most often is that a dietary deprivation in an animal model results in a suboptimal biological function that is preventable or reversible by an intake of physiological amounts of the element in question. Often the circumstantial evidence includes an identified essential function in a lower form of life, and biochemical actions consistent with a biological role or beneficial action in humans. The circumstantial evidence for essentiality is substantial for arsenic, boron, chromium, nickel, silicon, and vanadium. The evidence for essentiality for the... 

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