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.

Root Absorption and Transport Behavior of Technetium in Soybean

Abstract: The absorption characteristics and mechanisms of pertechnetate (TcO4−) uptake by hydroponically grown soybean seedlings (Glycine max cv Williams) were determined. Absorption from 10 micromolar solutions was linear for at least 6 hours, with 30% of the absorbed TcO4− being transferred to the shoot. Evaluation of concentration-dependent absorption rates from solutions containing 0.02 to 10 micromolar TcO4− shows the presence of multiphasic absorption isotherms with calculated Ks values of 0.09, 8.9, and 54 micromolar for intact seedlings. The uptake of TcO4− was inhibited by a 4-fold concentration excess of sulfate, phosphate, selenate, molybdate, and permanganate; no reduction was noted with borate, nitrate, tungstate, perrhenate, iodate, or vanadate. Analyses of the kinetics of interaction between TcO4− and inhibiting anions show permanganate to be a noncompetitive inhibitor, while sulfate, phosphate, and selenate, and molybdate exhibit characteristics of competitive inhibitors of TcO4− transport suggesting involvement of a common transport process.

Characterization of vanadate-based transition-state-analogue complexes of phosphoglucomutase by spectral and NMR techniques.

Abstract: Near ultraviolet spectral studies were conducted on two inhibitor complexes obtained by treating the dephospho form of the phosphoglucomutase{center dot}Mg{sup 2+} complex with inorganic vanadate in the presence of either glucose 1-phosphate or glucose 6-phosphate. Part of the spectral differences between the two inhibitor complexes arises because the glucose phosphate moiety in the complex derived from glucose 1-phosphate binds to the enzyme in a different way from the glucose phosphate moiety in the complex derived from glucose 6-phosphate and because these alternative binding modes produce different environmental effects on the aromatic chromophores of the dephospho enzyme. These spectra differences are strikingly similar to those induced by the binding of glucose 1-phosphate and glucose 6-phosphate to the phospho enzyme. {sup 31}P NMR studies of the phosphate group in these complexes also provide support for this binding pattern. Difference spectroscopy was used to resolve the spectrum of both inhibitor complexes to obtain the absorbance of their oxyvanadium chromophores. A spectrum more nearly like that of a normal vanadate ester is observed for the oxyvanadium chromophore in the corresponding complex involving glucose 1-phosphate and Li{sup +} instead of Mg{sup 2+}.

I. EFFECT OF ENZYME CONCENTRATION AND MODIFICATION ON LIPOSOME SIZE, INTRAMEMBRANE PARTICLE FORMATION AND Na+,K+-TRANSPORT

Abstract: + + K + ) - A TPase; Liposome size: Membrane reconstitution; Particle density; Freeze - fracture; (Rabbit kidney) Rabbit renal (Na++ K+)-ATPase (EC 3.6.1.3) was purified and incorporated into phosphatidylcholine liposomes. Freeze-fracture analysis of the reconstituted System reveals intramembrane particles formed by (Na+ + K + )-ATPase molecules which are randomly distributed on concave and convex fracture faces. The reconstituted (Na+ + K+)-ATPase performs active Na+,K +-transport. The distribution of particles as well as the rate of active transport are directly proportional to the (Na+ + K + )-ATPase protein concentration used for reconstitution, while the total amount of sodium and potassium ions exchanged by ATP per volume vesicle suspension reaches maximum when each vesicle contains on the average more than two particles. (Na+ + K + )-ATPase pretreated with ouabain or vanadate yields the same particle density and vesicle size as control enzyme. However, detergent-denatured enzyme loses its ability to form intramembrane particles or to increase the vesicle size indicating that the lipids surrounding the protein part of the molecule are essential for the reconstitution process. The vesicle diameter increases as a function of the number of particles per vesicle. Histograms of the size distribution become wider with increasing intramembrane particle density and tend to show more than one maximum.

Vanadate induces calcium signaling, Ca2+ release-activated Ca2+ channel activation, and gene expression in T lymphocytes and RBL-2H3 mast cells via thiol oxidation.

Abstract: Using ratiometric Ca 2+ imaging and patch-clamp measurement of Ca 2+ channel activity, we investigated Ca 2+ signaling induced by vanadium compounds in Jurkat T lymphocytes and rat basophilic leukemia cells. In the presence of external Ca 2+ , vanadium compounds produced sustained or oscillatory Ca 2+ elevations; in nominally Ca 2+ -free medium, a transient Ca 2+ rise was generated. Vanadate-induced Ca 2+ signaling was blocked by heparin, a competitive inhibitor of the 1,4,5-inositol trisphosphate (IP 3 ) receptor, suggesting that Ca 2+ influx is secondary to depletion of IP 3 -sensitive Ca 2+ stores. In Jurkat T cells, vanadate also activated the Ca 2+ -dependent transcription factor, NF-AT. Intracellular dialysis with vanadate activated Ca 2+ influx through Ca 2+ release-activated Ca 2+ (CRAC) channels with kinetics comparable to those of dialysis with IP 3 . Neither phosphatase inhibitors nor nonhydrolyzable nucleotide analogues modified CRAC channel activation. The action of vanadate, but not IP 3 , was prevented by the thiol-reducing agent DTT. In addition, the activation of CRAC channels by vanadate was mimicked by the thiol-oxidizing agent chloramine T. These results suggest that vanadate enhances Ca 2+ signaling via thiol oxidation of a proximal element in the signal transduction cascade.