title: Purification and characterization of an alkaliphilic choline oxidase of Fusarium oxysporum.
abstract: A novel choline oxidase found in a fungus, Fusarium oxysporum strain V2, was purified to homogeneity as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The enzyme has a molecular mass of 128 kDa and consists of two identical subunits. The purified enzyme showed adsorption peaks at 340 nm and 450 nm. It showed alkaliphilic pH characteristics: its optimum pH was 9.0-10.0, and it was stable at pH 8.0-10.2. The Michaelis constant (Km) values for choline and betaine aldehyde were 0.28 mM and 0.39 mM respectively. Trimethylamino-alcohols, dimethylamino-alcohols, and diethylaminoethanol were substrates for the enzyme, but the Km values for them increased with decreasing numbers of methyl groups on the ammonium headgroup. A marked decrease in the maximum velocity (Vmax) and Vmax/Km values was observed when N-replaced choline analogs were used as substrate instead of choline. The enzyme had a remarkably higher affinity for choline and betaine aldehyde than do previously reported enzymes. The enzyme oxidized these two substrates more quickly than a choline oxidase from Arthrobacter globiformis, and oxidation by the V2 enzyme was accompanied by an increase in the stoichometric amount of hydrogen peroxide.
authors.affiliation: Department of Entrepreneurship and Management, School of Business Administration, University of Hyogo, Hyogo, Japan. enoki@biz.u-hyogo.ac.jp
authors.forename: Shogo
authors.initials: S
authors.lastname: Enokibara
mesh_terms: D000429:Alcohol Oxidoreductases / Q000096:biosynthesis / Q000302:isolation & purification* / Q000378:metabolism*; D002794:Choline / Q000378:metabolism; D005670:Fusarium / Q000201:enzymology* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents / Q000494:pharmacology; D008670:Metals / Q000494:pharmacology; D010084:Oxidation-Reduction; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D007202:Indicators and Reagents; D008670:Metals; D000429:Alcohol Oxidoreductases; C019888:choline oxidase; D002794:Choline