Biological systems vanadate

Gresser MJ, Tracey AS (1990) Vanadates as Phosphate Analogs in Biochemistry. In Chastcen ND (ed) Vanadium in Biological Systems. Physiology and Biochemistry. Kluwer Academic, Dordrecht, p 63... 

Gresser, M.J., A.S. Tracey, and N.D. Chasteen. 1990. Vanadates as phosphate analogs in biochemistry. Vanadium in biological systems. Dordrecht, Boston, London Kluwer Academic Publishers, pp 63-79. 

Extrapolating from well-characterized enzymatic inhibition in test tubes, numerous mechanistic ideas concerning the in vivo effects of vanadium compounds have been advanced. The effects of vanadium compounds as transition-state analogs of certain enzymes with a phosphoprotein intermediate in their reaction scheme is proposed to account for the action of vanadium [11] in many biological systems. Unfortunately, it is often difficult to determine if the inhibition observed in the test tube occurs in vivo. For example, although vanadate is a potent inhibitor of plasma membrane ion pumps (such as the sodium potassium ATPase) in the test tube, it is difficult to determine if these pumps are actually inhibited in animals exposed to vanadium compounds. Currently, the role of vanadium compounds as protein phosphatase (PTP) inhibitors is believed to be related to the metabolic effects of this... 

Plass, W. (1999). Phosphate and vanadate in biological systems chemical relatives or more Angewandte Chemie, 38, 909-912. 

Applications to specific biological systems containing vanadium will be addressed in some detail in the context of the respective subsections of Chapter 4 on naturally occurring vanadium compounds vanadium in sea squirts (e.g. Figure 4.3), vanadate-dependent haloperoxidases (e.g. Table 4.5) and vanadium nitrogenases (e.g. Table 4.8). The central messages, including key references, are briefly summarised here. 

Absorption of orally administered vanadium compounds has been measured by Cantley and coworkers while investigating the intracellular inhibition of (Na,K)-ATPase activity by sodium vanadate in human erythrocytes [81], They noted that a significant portion of the administered vanadium was in a form not capable of inhibitory activity. EPR spectra of NaVOs-treated erythrocytes showed a characteristic spectrum, indicating that reduction of V(V) to V(IV) had occurred. In one hour, approximately 30% of the added vanadate was reduced, but only vanadium contained within the cells had undergone reduction. Thus, absorption of vanadate, likely fluough a cation transport system, must occur before biological reduction could occur [62]. Further study of this reaction by EPR showed... 

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