Publication: Oxidation mode of pyranose 2-oxidase is controlled by pH
Issued Date
2013-02-26
Resource Type
ISSN
15204995
00062960
00062960
Other identifier(s)
2-s2.0-84874446813
Rights
Mahidol University
Rights Holder(s)
SCOPUS
Bibliographic Citation
Biochemistry. Vol.52, No.8 (2013), 1437-1445
Suggested Citation
Methinee Prongjit, Jeerus Sucharitakul, Bruce A. Palfey, Pimchai Chaiyen Oxidation mode of pyranose 2-oxidase is controlled by pH. Biochemistry. Vol.52, No.8 (2013), 1437-1445. doi:10.1021/bi301442x Retrieved from: https://repository.li.mahidol.ac.th/handle/20.500.14594/31364
Research Projects
Organizational Units
Authors
Journal Issue
Thesis
Title
Oxidation mode of pyranose 2-oxidase is controlled by pH
Other Contributor(s)
Abstract
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 H 2O2. 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 pKa 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. © 2013 American Chemical Society.