Choline Oxidase from Alcaligenes sp.

Unit definition.
Under the condition of 37 ℃ and pH8.0, the amount of 1mmol hydrogen peroxide produced by choline was 1 unit per minute. Note: during the conversion of choline to betaine by choline oxidase, 2 umol of H2O2 is produced per 1umol of choline.

Application.
Choline oxidase from Alcaligenes has been used in a study of choline biosensors constructed from chitin membranes and their application in measuring cholinesterase inhibitory activity. Choline oxidase from Alcaligenes has been used to study the photoresponse of covalently bound flavin to choline oxidase.

Physical property.
Isoelectric point: 4.1 ±0.1; Michaelis constant: 2.84 x 103M (choline), 5.33x 103M (betaaldehyde); structure: 1mol FAD covalently binds with 1mol; inhibitors: p-chloromercuric benzoic acid, Cu + +, Co + +, Hg + +, Ag +; optimum pH: 8.0-8.5; optimum temperature: 40-45 °C; pH stability: pH7.0-9.0 (30 °C for 2 hours). Thermal stability: less than 37 °C (pH 7.5 for 10 minutes).

Biochemical / physiological behavior.
Choline oxidase catalyzes the four-electron oxidation of choline to betaine, in which betaaldehyde is the intermediate and molecular oxygen is the main electron acceptor. The enzyme can also accept betaaldehyde as substrate. This allows us to study the conversion of choline to aldehyde intermediates and the reaction mechanism of the conversion of betaine to betaine. The enzyme is a flavoprotein with a molecular weight of about 72000Da (gel filtration) or 66000Da (SDS gel electrophoresis).