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Inhibition of (Na,K)-ATPase by tetravalent vanadium. J Biol Chem 1984 Apr 25;259(8):4971-8

Date

04/25/1984

Pubmed ID

6325413

Scopus ID

2-s2.0-0021358955 (requires institutional sign-in at Scopus site)   31 Citations

Abstract

Vanadyl, the tetravalent state of vanadium and a divalent cation, VO2+, was a relatively powerful inhibitor of highly purified membrane-bound sodium and potassium ion transport adenosine triphosphatase. The sensitivity of the ATPase activity to vanadyl characteristically correlated positively with the specific activity of the enzyme preparation. Inhibition ranged from nearly complete inhibition at less than 5 microM vanadyl for some of the purest fractions (specific activity approximately 45 mumol/min/mg of protein) to no observable inhibition at 300 microM vanadyl in one crude preparation of the enzyme with a specific activity of 10 mumol/min/mg of protein. The level of free vanadyl was reduced by incubation with these membranes, but this reduction was not sufficient to account for the low sensitivity to vanadyl observed in crude preparations. A reduction in specific activity by partial inactivation of a sensitive preparation by treatment with FeCl3 and ascorbate reduced its sensitivity to vanadyl. Anionic ligands of the enzyme, vanadate or ATP, increased the rate of recovery from inhibition after chelation of free vanadyl. At pH 6.1, the inhibition was characteristically fully reversible (t1/2 approximately 10 min), whereas at pH 8.1 it was stable for hours. The degree and stability of enzyme inhibition by vanadyl increased for several hours during incubation of the vanadyl-enzyme mixture, and at pH 6.1 the properties of the inhibitor itself also changed with time. Preincubation of the ion at that pH for 5 h before addition of the enzyme produced a more stable inhibition. The time- and pH-dependent changes in the degree and stability of enzyme inhibition probably relate to the complex chemistry of the vanadyl ion in solution.

Author List

North P, Post RL

Author

Paula E. North MD, PhD Professor in the Pathology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Animals
Cell Membrane
Dogs
Kidney
Kinetics
Magnesium
Oxidation-Reduction
Potassium
Sodium-Potassium-Exchanging ATPase
Swine
Vanadates
Vanadium