Purification and Characterization of Choline Oxidase from Arthrobacter globiformis

Choline oxidase was purified from the cells of Arthrobacter globiformis by fractionations with acetone and ammonium sulfate, and column chromatographies on DEAE-cellulose and on Sephadex G-200. The purified enzyme preparation appeared homogeneous on disc gel electrophoresis. The enzyme was a fiavoprotein having a molecular weight of approx. 83, 000 (gel filtration) or approx. 71, 000 (sodium dodecyl sulfate-polyacrylamide disc gel electrophoresis) and an isoelectric point (pI) around pH 4.5. Identification of the reaction products showed that the enzyme catalyzed the following reactions: choline+O2→betaine aldehyde+H2O2, betaine aldehyde+O2+H2O→betaine+H2O2. The enzyme was highly specific for choline and betaine aldehyde (relative reaction velocities: choline, 100%; betaine aldehyde, 46%; N, N-dimethylaminoethanol, 5.2%; triethanolamine, 2.6%; diethanolamine, 0.8%; monoethanolamine, N-methylaminoethanol, methanol, ethanol, propanol, formaldehyde, acetaldehyde, and propionaldehyde, 0%), Its Km values were 1.2mM for choline and 8.7mM for betaine aldehyde. The optimum pH for the enzymic reaction was around pH 7.5.