2wd4
Ascorbate Peroxidase as a heme oxygenase: w41A variant product with t-butyl peroxideAscorbate Peroxidase as a heme oxygenase: w41A variant product with t-butyl peroxide
Structural highlights
FunctionEvolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe heme peroxidases and heme oxygenase enzymes share a common heme prosthetic group but catalyse fundamentally different reactions, the first being H2O2-dependent oxidation of substrate using an oxidised Compound I intermediate, the second O2-dependent degradation of heme. It has been proposed that these enzymes utilise a common reaction intermediate, a ferric hydroperoxide species, that sits at a crossroads in the mechanism and beyond which there are two mutually exclusive mechanistic pathways. Here, we present evidence to support this proposal in a heme peroxidase. Hence, we describe kinetic data for a variant of ascorbate peroxidase (W41A) which reacts slowly with t-butylhydroperoxide and does not form the usual peroxidase Compound I intermediate; instead, structural data show that a product is formed in which the heme has been cleaved at the alpha-meso position, analogous to the heme oxygenase mechanism. We interpret this to mean that the Compound I (peroxidase) pathway is shut down, so that instead the reaction intermediate diverts through the alternative (heme oxygenase) route. A mechanism for formation of the product is proposed and discussed in the light of what is known about the heme oxygenase reaction mechanism. Evidence for Heme Oxygenase Activity in a Heme Peroxidase.,Raven E, Badyal S, Eaton G, Mistry S, Pipirou Z, Basran J, Metcalfe C, Gumiero A, Handa S, Moody P Biochemistry. 2009 Mar 23. PMID:19309109[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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