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A mechanism for NADPH inhibition of catalase compound II formation
Author(s) -
Hillar A.,
Nicholls P.
Publication year - 1992
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(92)80969-n
Subject(s) - catalase , mechanism (biology) , chemistry , biophysics , biochemistry , stereochemistry , combinatorial chemistry , enzyme , biology , physics , quantum mechanics
Catalase‐bound NADPH both prevents and reverses the accumulation of inactive bovine liver catalase peroxide compound II generated by ‘endogenous’ donors under conditions of steady H 2 O 2 formation without reacting rapidly with either compound I or compound II. It thus differs both from classical 2‐electron donors of the ethanol type, and from 1‐electron donors of the ferrocyanide/phenol type. NADPH also inhibits compound II formation induced by the exogenous one‐electron donor ferrocyanide. A catalase reaction scheme is proposed in which the initial formation of compound II from compound I involves production of a neighbouring radical species. NADPH blocks the final formation of stable compound II by reacting as a 2‐electron donor to compound II and to this free radical. The proposed behaviour resembles that of labile free radicals formed in cytochrome c peroxidase and myoglobin. Such radical migration patterns within haem enzymes are increasingly common motifs.