ISSN:
1573-4919
Keywords:
glutathione reductase
;
Saccharomyces cerevisiae
;
redox interconversion
;
metals
;
cell-free extracts
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Summary Redox inactivation of glutathione reductase involves metal cations, since chelators protected against NADPH-inactivation, 3 µM EDTA or 10 µM DETAPAC yielding full protection. Ag+, Zn2+ and Cd2+ potentiated the redox inactivation promoted by NADPH alone, while Cr3+, Fe2+, Fe3+, Cu+, and Cu2+ protected the enzyme. The Zn2+ and Cd2+ effect was time-dependent, unlike conventional inhibition. Glutathione reductase interconversion did not require dioxygen, excluding participation of active oxygen species produced by NADPH and metal cations. One Zn2+ ion was required per enzyme subunit to yield full NADPH-inactivation, the enzyme being reactivated by EDTA. Redox inactivation of glutathione reductase could arise from the blocking of the dithiol formed at the active site of the reduced enzyme by metal cations, like Zn2+ or Cd2+. The glutathione reductase activity of yeast cell-free extracts was rapidly inactivated by low NADPH or moderate NADH concentrations; NADP+ also promoted rapid inactivation in fresh extracts, probably after reduction to NADPH. Full inactivation was obtained in cell-free extracts incubated with glucose-6-phosphate or 6-phosphogluconate; the inactivating efficiency of several oxidizable substrates was directly proportional to the specific activities of the corresponding dehydrogenases, confirming that redox inactivation derives from NADPH formed in vitro.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00229534
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