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Title: Kinetics and mechanism of reduction of ferricytochrome c by glutathione and L-cysteine: A comparative study
Authors: Subudhi, U
Chainy, G B N
Mohanty, P
Keywords: Ferricytochrome c;Glutathione;L-cysteine;Reduction
Issue Date: Feb-2006
Publisher: CSIR
IPC Code: C07K14/80
Abstract: The kinetics and mechanism of the reduction of ferricytochrome c [Cyt c(III)] by substrates namely glutathione (GSH) and L-cysteine (L-cys) have been investigated spectrophotometrically employing [substrate]T >> [Cyt c(III)]T. The reaction exhibits first order dependence in [substrate]T and [Cyt c(III)]T. The pseudo-first order rate constant increases with an increase in pH, indicating that the conjugate base form of the HCyt c(III) is a better oxidant than the parent HCyt c(III). The electron transfer rate constants between the oxidants and GSH for both the k₁ and k₂ paths are found to be greater than that with L-cysteine. Hence, GSH is a better reductant of Cyt c(III) as compared to L-cysteine. A suitable mechanism has been proposed on the basis of experimental findings. The deprotonation constant for HCyt c(III) and the second order rate constants of k₁ and k₂ paths for the present reaction at 25ºC have been determined.
Page(s): 37-40
ISSN: 0301-1208
Appears in Collections:IJBB Vol.43(1) [February 2006]

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