Document Detail

Oxidation mode of pyranose 2-oxidase is controlled by pH.
MedLine Citation:
PMID:  23356577     Owner:  NLM     Status:  MEDLINE    
Pyranose 2-oxidase (P2O) from Trametes multicolor is a flavoenzyme that catalyzes the oxidation of d-glucose and other aldopyranose sugars at the C2 position by using O₂ as an electron acceptor to form the corresponding 2-keto-sugars and H₂O₂. In this study, the effects of pH on the oxidative half-reaction of P2O were investigated using stopped-flow spectrophotometry. The results showed that flavin oxidation occurred via different pathways depending on the pH of the environment. At pH values lower than 8.0, reduced P2O reacts with O₂ to form a C4a-hydroperoxyflavin intermediate, leading to elimination of H₂O₂. At pH 8.0 and higher, the majority of the reduced P2O reacts with O₂ via a pathway that does not allow detection of the C4a-hydroperoxyflavin, and flavin oxidation occurs with decreased rate constants upon the rise in pH. The switching between the two modes of P2O oxidation is controlled by protonation of a group which has a pK(a) of 7.6 ± 0.1. Oxidation reactions of reduced P2O under rapid pH change as performed by stopped-flow mixing were different from the same reactions performed with enzyme pre-equilibrated at the same specified pH values, implying that the protonation of the group which controls the mode of flavin oxidation cannot be rapidly equilibrated with outside solvent. Using a double-mixing stopped-flow experiment, a rate constant for proton dissociation from the reaction site was determined to be 21.0 ± 0.4 s⁻¹.
Methinee Prongjit; Jeerus Sucharitakul; Bruce A Palfey; Pimchai Chaiyen
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2013-02-12
Journal Detail:
Title:  Biochemistry     Volume:  52     ISSN:  1520-4995     ISO Abbreviation:  Biochemistry     Publication Date:  2013 Feb 
Date Detail:
Created Date:  2013-02-27     Completed Date:  2013-04-15     Revised Date:  2014-02-27    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1437-45     Citation Subset:  IM    
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MeSH Terms
Carbohydrate Dehydrogenases / metabolism*
Hydrogen-Ion Concentration
Oxygen / metabolism
Trametes / enzymology*
Grant Support
Reg. No./Substance:
0/Protons; EC 1.1.-/Carbohydrate Dehydrogenases; EC oxidase; S88TT14065/Oxygen

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