Interactions of oxovanadates and selected oxomolybdates with proteins

The interactions of phosphoglucose isomerase with solutions of rapidly interconverting oxovanadates are described. Quantitative speciation analyses of vanadate monomer, dimer, tetramer and pentamer were performed under the conditions of the enzyme assay. 2D EXSY⁵¹V NMR spectroscopy was used to demonstrate that the oligoanions are sufficiently long-lived to be recognized by the enzyme as different species. The observations are consistent with the vanadate tetramer being responsible for the observed inhibition. Selected oxomolybdates ([(CH₃)₂AsMo₄OH]^2– and [(NH₃C₂H₄P)₂Mo₅O₂₁]^2–) were also found to inhibit 6-phosphogluconate dehydrogenase, glucose-6-phosphate dehydrogenase, glycerol-3-phosphate dehydrogenase and fructose-1,6-bisphosphate aldolase. The selectivities and affinities of these proteins for the oxometalates are discussed.