Title of article :
Reactivity of biologically important thiol compounds with superoxide and hydrogen peroxide
Author/Authors :
Christine C. Winterbourn، نويسنده , , Diana Metodiewa، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 1999
Pages :
7
From page :
322
To page :
328
Abstract :
The reactivities of glutathione, cysteine, cysteamine, penicillamine, N-acetylcysteine, dithiothreitol and captopril with superoxide generated from xanthine oxidase and hypoxanthine, and with reagent hydrogen peroxide, have been investigated. Rates of thiol loss on adding hydrogen peroxide, and superoxide-dependent thiol loss and oxygen uptake were measured. The relative reactivities of the different thiols with both oxidants were inversely related to the pK of the thiol group, such that at pH 7.4, penicillamine was the most reactive, N-acetylcysteine weakly reactive and no reaction was seen with captopril. For hydrogen peroxide, the calculated rate constants for the reaction with the thiolate anion all fell within the range 18–26 M−1 s−1. With superoxide, our results are consistent with each thiol reacting via a short chain that consumes oxygen and regenerates superoxide. Only with some of the thiols, was the consumed oxygen recovered as hydrogen peroxide. Reported values for the rate constant for the reaction of thiols with superoxide vary over four orders of magnitude, with the highest being >105 M−1 s−1. Due to the complexity of the chain reaction, no study so far has been able to obtain accurate values and we consider the best estimates to be in the 30 to 1000 M−1 s−1 range.
Keywords :
Cysteine , free radicals , glutathione , Thiyl radicals , thiols , Reaction with superoxide and hydrogen peroxide superoxide , Reaction with thiols , hydrogen peroxide , Reaction with thiols , N-acetylcysteine
Journal title :
Free Radical Biology and Medicine
Serial Year :
1999
Journal title :
Free Radical Biology and Medicine
Record number :
518255
Link To Document :
بازگشت