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Hydrogen peroxide oxidation by catalase‐peroxidase follows a non‐scrambling mechanism
Author(s) -
Vlasits Jutta,
Jakopitsch Christa,
Schwanninger Manfred,
Holubar Peter,
Obinger Christian
Publication year - 2007
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/j.febslet.2006.12.037
Subject(s) - chemistry , hydrogen peroxide , peroxidase , catalase , synechocystis , redox , heme , stereochemistry , peroxide , reaction mechanism , bifunctional , enzyme , medicinal chemistry , catalysis , inorganic chemistry , organic chemistry , biochemistry , mutant , gene
Despite catalyzing the same reaction (2H 2 O 2 → 2H 2 O + O 2 ) heme‐containing monofunctional catalases and bifunctional catalase‐peroxidases (KatGs) do not share sequence or structural similarities raising the question of whether or not the reaction pathways are similar or different. The production of dioxygen from hydrogen peroxide by monofunctional catalases has been shown to be a two‐step process involving the redox intermediate compound I which oxidizes H 2 O 2 directly to O 2 . In order to investigate the origin of O 2 released in KatG mediated H 2 O 2 degradation we performed a gas chromatography–mass spectrometry investigation of the evolved O 2 from a 50:50 mixture of H 2 18 O 2 /H 2 16 O 2 solution containing KatGs from Mycobacterium tuberculosis and Synechocystis PCC 6803. The GC–MS analysis clearly demonstrated the formation of 18 O 2 ( m / e = 36) and 16 O 2 ( m / e = 32) but not 16 O 18 O ( m / e = 34) in the pH range 5.6–8.5 implying that O 2 is formed by two‐electron oxidation without breaking the O–O bond. Also active site variants of Synechocystis KatG with very low catalase but normal or even enhanced peroxidase activity (D152S, H123E, W122F, Y249F and R439A) are shown to oxidize H 2 O 2 by a non‐scrambling mechanism. The results are discussed with respect to the catalatic mechanism of KatG.