Phospho vanadates

Deng et al. (1993,1998) and Ray et al. (1993) have used V " as an analogue of in an attempt to model the transition state of the hydrolysis of phospho-diesters by ribonuclease A since is assumed to adopt the expected five coordination more readily than Examination of the vibrational spectrum of the vanadate analogue indicates that the terminal V-O bonds are only slightly weakened when bonded to the protein. A quantitative bond valence analysis effectively rules out two proposed mechanisms that involve the protonation of the terminal O atoms. 

Figure 6. 51V NMR spectra of 0.5, 1.0, and 5.0 mM total vanadate in 150 mM imidazole at pH 8.0. The V2 (—555 ppm) and V4 (—579 ppm) resonances are indicated by arrows. The V2 resonance (—573 ppm) is upfield of the Vj and downfield of the V4 resonance, and the V5 resonance (—585 ppm) is furthest upfield. The H+-dependent equilibrium constants K12 and K14 are defined, and plots of [V2] as a function of [ V2]2 and [V4] as a function of [V2]4 are shown for a study carried out at constant ionic strength. The data shown in these plots were reported previously as assay conditions for studies of 6-phospho gluconate dehydrogenase from sheep liver (Data are from reference 35).

Four examples of structurally characterised, vanadate-inhibited phosphorylation enzymes working on the hydrolysis of phospho-ester bonds in nucleotides I, the vanadate-uridine complex of bovine pancreatic ribonuclease-A II, the vanadate complex of ribonuclease-Tj from the fungus Aspergillus oryzae-. III, the vanadate-uridine complex of cyclic nucleotide phosphodiesterase from the cruciferous plant Arabidopsis thaliana-, IV, human tyrosyl-DNA phosphodiesterase (Ur = uridine). 

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