Pervanadates

For in vitro studies there are a number of compounds available to block protein phosphatase activity. Phosphate buffers inactivate all of these enzymes. Several naturally occurring toxins are potent inhibitors of PPPs, e.g., okadaic acid or microcystin, and are frequently used tools. PPM and PTP family members are not affected by these toxins. Vanadate containing solutions are competitive inhibitors of PTPs, pervanadate is an irreversible inhibitor of PTPs. 

In an excess of concentrated (30 per cent) hydrogen peroxide to which a little sulfuric acid has been added to insure acidity, dissolve the potassium metavanadate, observing that the color changes to an intense yellow. To this solution, well cooled, add 95 per cent alcohol until the pervanadate has been precipitated as a microcrystalline powder. Filter off the product, wash with alcohol, and dry in a desiccator over calcium chloride. 

Concentrated acid solutions of vanadium pentoxide are reduced to the tetravalent state by hydrogen peroxide, the peroxides of sodium, barium, magnesium, and by persulphates of potassium and ammonium.4 Acid solutions of vanadium pentoxide give rise to pervanadic acid with hydrogen peroxide. 

The yellow compound V02(0H)3 thus formed can be looked upon as a hydrated pervanadic acid, HVQ4.H20, or as peroxyorthovanadic acid,1... 

Pervanadic acid appears, therefore, to be formed from metavanadic acid, HVOa. This view of the reaction and the formula for pervanadic acid are further supported by titrating the red solution with caustic soda, when it is found that two molecules of caustic soda are required for each molecule of vanadium pentoxide. The monobasicity of the acid is confirmed by measuring the equivalent conductivities of solutions of potassium pervanadate. 

It is not attacked by dilute sulphuric acid in the cold, but on warming the mixture hydrogen peroxide is formed. Pervanadic acid, on the other hand, is decomposed by cold dilute sulphuric acid. Pemiobic acid occupies an intermediate position in the order of stability.1... 

Huyer, G., S. Liu, J. Kelly, J. Moffat, P. Payette, B. Kennedy, G. Tsaprailis, M.J. Gresser, and C. Ramachandran. 1997. Mechanism of inhibition of protein-tyrosine phosphatases by vanadate and pervanadate. J. Biol. Chem. 272 843-851. 

Huyer, G. 1997. Mechanism of inhibition of protein tyrosine phosphatases by vanadate and pervanadate. J. Biolog. Chem. 272 843-851. 

Tsiani, E., E. Bogdanovic, A. Sorisky, L. Nagy, and I.G. Fantus. 1998. Tyrosine phosphatase inhibitors, vanadate and pervanadate, stimulate glucose transport and GLUT translocation in muscle cells by a mechanism independent of phosphatidyli-nositol 3-kinase and protein kinase C. Diabetes 47 1676-1686. 

Zhao, Z., Tan, Z., Diltz, C. D., You, M., and Fischer, E. H. (1996). Activation of mitogen-activated protein (MAP) kinase pathway by pervanadate, a potent inhibitor of tyrosine phosphatases. J. Biol. Chem. 271, 22251-22255. 

Figure 1.9 Spectrum a Difference spectrum for 300 p.M peroxo-VCPO minus holo-VCPO. Spectrum b Difference spectrum for 300 /(M pervanadate minus vanadate. Source Renirie, R., Hemrika, W., Piersma, S.R. and Wever, R. (2000). Biochemistry, 39, 1133-1141. Reprinted with permission from The American Chemical Society 2000.

The activation of IKK is considered a major mechanism of NF-kB activation in the classical pathway. However, in certain cases, such as in response to shortwave UV light (Li and Karin, 1998 Kato et al., 2003), pervanadate (Mukhopadhyay et al.,... 

PUMKLIA KM, LAU L-F, Huang C-K, Burroughs S, FEINSTEIN MB. Activation of signal transduction in platelets by the rosine phosphatase inhibitor pervanadate (vanadyl hydre reraxide). Biochem J286 441-449, 1992. 

Treatment of the epoxide 4, prepared by treatment of humulene with pervanadic acid (H2O2-V2O5), with 1.8 M sulfuric acid and acetone (1 1) at O C for 30 minutes gave the diol 5 as the sole product in 95% yield. ... 

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