Vanadate

About: Vanadate is a research topic. Over the lifetime, 4497 publications have been published within this topic receiving 120109 citations. The topic is also known as: vanadate.

Use of vanadate as protein-phosphotyrosine phosphatase inhibitor.

Abstract: Publisher Summary This chapter discusses the use of vanadate as protein-phosphotyrosine phosphatase inhibitor. Vanadium ions have found widespread use as an inhibitor of protein-phosphotyrosine phosphatases. Some form of vanadium ion is added to preserve the phosphotyrosine content of cells, cell lysates, and tyrosine kinase assays. Protein-phosphotyrosine phosphatase (PPTPase) activity is found in most mammalian and avian cells and tissues as well as in bacterial and yeast cultures. This uncertainty in substrate suitability may influence the effectiveness of inhibitors. The multiple phosphotyrosine phosphatases may be more or less sensitive to the same inhibitor. The protein-phosphotyrosine phosphatase activities sensitive to inhibition by zinc chloride and sodium orthovanadate are conveniently separable from the phosphoseryl and phosphothreonyl phosphatase activities inhibited by EDTA and fluoride.

Insulin-like stimulation of glucose oxidation in rat adipocytes by vanadyl (IV) ions

Abstract: The mechanism of insulin action is still unknown1. One approach to this problem is to apply substances which mimic the action of the hormone to target cells. Ouabain and deprivation of extracellular K+ (refs 2,3), which inhibit the active transport of Na+ and K+ ions, are both known to activate glucose transport and oxidation in isolated adipocytes. Vanadate (V) ions have recently been shown to act as very efficient inhibitors of the sodium pump or (Na+ + K+)ATPase in in vitro preparations4. They have a natriuretic and diuretic effect in rats5 and a positive inotropic effect on cat heart muscle6. Many tissues contain vanadium at a concentration of about 0.1–1.0 μM (ref. 7) and so endogenous vanadate could be a physiological regulator of the sodium pump. But this is still open to debate, because the bulk of the vanadium is probably in the vanadyl (IV) form8,9 and VO2+ ions bind tightly to proteins8,10. VO2+ is a relatively ineffective inhibitor of (Na+ + K+) ATPase in vitro8,11. We report here that externally applied vanadate ions at low concentrations mimic fully the effect of insulin on glucose oxidation in rat adipocytes. However, this simulation seems to be due mainly to the effects of vandyl (IV) ions, probably produced within the cells, and not primarily to inhibition of the sodium pump. Also, externally applied vanadyl (IV) ions stimulate glucose oxidation substantially. Vanadyl ions are known to be powerful inhibitors of alkaline phosphatase12 and we therefore consider the possibility that they inhibit a cellular phosphatase activity. An early event in insulin action may involve alteration of the degree of phosphorylation of protein(s) involved in regulation of sugar transport.

Uptake of Metal Ions by Rhizopus arrhizus Biomass

Abstract: Rhizopus arrhizus biomass was found to absorb a variety of different metal cations and anions but did not absorb alkali metal ions. The amount of uptake of the cations was directly related to ionic radii of La3+, Mn2+, Cu2+, Zn2+, Cd2+, Ba2+, Hg2+, Pb2+, UO22+, and Ag+. The uptake of all the cations is consistent with absorption of the metals by sites in the biomass containing phosphate, carboxylate, and other functional groups. The uptake of the molybdate and vanadate anions was strongly pH dependent, and it is proposed that the uptake mechanism involves electrostatic attraction to positively charged functional groups.

X-ray structure of the magnesium(II).ADP.vanadate complex of the Dictyostelium discoideum myosin motor domain to 1.9 A resolution.

Abstract: The structure of the vanadate-trapped ADP complex of a truncated head of Dictyostelium myosin II consisting of residues Asp 2-Asn 762 has been determined by molecular replacement at 1.9 A resolution and refined to a crystallographic R-factor of 19.4%. The crystals belong to the orthorhombic space group C2221 where a = 84.50 A, b = 145.4 A, and c = 152.8 A. The conformation of the protein is similar to that of MgADP.AlF4.SlDc [Fisher, A.J., et al. (1995) Biochemistry 34, 8960-8972]. The nucleotide binding site contains a complex between MgADP and vanadate where MgADP exhibits a very similar conformation to that seen in previous complexes. The vanadate ion adopts a trigonal bipyramidal coordination. The three equatorial oxygen ligands are fairly short, average 1.7 A, relative to a single bond distance of approximately 1.8 A and are coordinated to the magnesium ion, N zeta of Lys 185, and five other protein ligands. The apical coordination to the vanadate ion is filled by a terminal oxygen on the beta-phosphate of ADP and a water molecule at bond distances of 2.1 and 2.3 A, respectively. The long length of the apical bonds suggests that the bond order is considerably less than unity. This structure confirms the earlier suggestion that vanadate is a model for the transition state of ATP hydrolysis and thus provides insight into those factors that are responsible for catalysis. In particular, it shows that the protein ligands and water structure surrounding the gamma-phosphate pocket are oriented to stabilize a water molecule in an appropriate position for in-line nucleophilic attack on the gamma-phosphorus of ATP. This structure reveals also an orientation of the COOH-terminal region beyond Thr 688 which is very different from that observed in either MgADP.BeFx.SlDc or chicken skeletal myosin subfragment 1. This is consistent with the COOH-terminal region of the molecule playing an important role in the transduction of chemical energy of hydrolysis of ATP into mechanical movement.