[CHOX_ARTGO] Catalyzes the two-step oxidative conversion of choline to glycine-betaine with betaine aldehyde as an intermediate. Glycine-betaine accumulates to high levels in the cytoplasm of cells to prevent dehydration and plasmolysis in adverse hyperosmotic environments. Accepts either choline or the reaction intermediate betaine-aldehyde as substrate.[1]
Evolutionary Conservation
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Publication Abstract from PubMed
The oxidation of choline catalyzed by choline oxidase includes two reductive half-reactions where FAD is reduced by the alcohol substrate and by an aldehyde intermediate transiently formed in the reaction. Each reductive half-reaction is followed by an oxidative half-reaction where the reduced flavin is oxidized by oxygen. Here, we have used mutagenesis to prepare the Ser101Ala mutant of choline oxidase and have investigated the impact of this mutation on the structural and kinetic properties of the enzyme. The crystallographic structure of the Ser101Ala enzyme indicates that the only differences between the mutant and wild-type enzymes are the lack of a hydroxyl group on residue 101 and a more planar configuration of the flavin in the mutant enzyme. Kinetics established that replacement of Ser101 with alanine yields a mutant enzyme with increased efficiencies in the oxidative half-reactions and decreased efficiencies in the reductive half-reactions. This is accompanied by a significant decrease in the overall rate of turnover with choline. Thus, this mutation has revealed the importance of a specific residue for the optimization of the overall turnover of choline oxidase, which requires fine-tuning of four consecutive half-reactions for the conversion of an alcohol to a carboxylic acid.
Structural and kinetic studies on the Ser101Ala variant of choline oxidase: Catalysis by compromise.,Finnegan S, Yuan H, Wang YF, Orville AM, Weber IT, Gadda G Arch Biochem Biophys. 2010 Sep 15;501(2):207-213. Epub 2010 Jun 16. PMID:20561507[2]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
↑Rand T, Halkier T, Hansen OC. Structural characterization and mapping of the covalently linked FAD cofactor in choline oxidase from Arthrobacter globiformis. Biochemistry. 2003 Jun 17;42(23):7188-94. PMID:12795615 doi:https://dx.doi.org/10.1021/bi0274266
↑Finnegan S, Yuan H, Wang YF, Orville AM, Weber IT, Gadda G. Structural and kinetic studies on the Ser101Ala variant of choline oxidase: Catalysis by compromise. Arch Biochem Biophys. 2010 Sep 15;501(2):207-213. Epub 2010 Jun 16. PMID:20561507 doi:10.1016/j.abb.2010.06.014
