Reaction: choline + 2 O2 + H2O = betaine + 2 H2O2 (overall reaction)
(1a) choline + O2 = betaine aldehyde + H2O2
(1b) betaine aldehyde + O2 + H2O = betaine + H2O2
Glossary: choline = (2-hydroxyethyl)trimethylammonium
betaine aldehyde = N,N,N-trimethyl-2-oxoethylammonium
betaine = glycine betaine = N,N,N-trimethylammonioacetate
Systematic name: choline:oxygen 1-oxidoreductase
Comments: A flavoprotein (FAD). In many bacteria, plants and animals, the osmoprotectant betaine is synthesized using different enzymes to catalyse the conversion of (1) choline into betaine aldehyde and (2) betaine aldehyde into betaine. In plants, the first reaction is catalysed by EC 1.14.15.7EC 1.14.15.7, choline monooxygenase, whereas in animals and many bacteria, it is catalysed by either membrane-bound choline dehydrogenase (EC 1.1.99.1) or soluble choline oxidase (EC 1.1.3.17) [6]. The enzyme involved in the second step, EC 1.2.1.8, betaine-aldehyde dehydrogenase, appears to be the same in those plants, animals and bacteria that use two separate enzymes.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 9028-67-5
References:
1. Ikuta, S., Imamura, S., Misaki, H. and Horiuti, Y. Purification and characterization of choline oxidase from Arthrobacter globiformis. J. Biochem. (Tokyo) 82 (1977) 1741-1749. [PMID: 599154]
2. Rozwadowski, K.L., Khachatourians, G.G. and Selvaraj, G. Choline oxidase, a catabolic enzyme in Arthrobacter pascens, facilitates adaptation to osmotic stress in Escherichia coli. J. Bacteriol. 173 (1991) 472-478. [PMID: 1987142]
3. Rand, T., Halkier, T. and Hansen, O.C. Structural characterization and mapping of the covalently linked FAD cofactor in choline oxidase from Arthrobacter globiformis. Biochemistry 42 (2003) 7188-7194. [PMID: 12795615]
4. Gadda, G., Powell, N.L. and Menon, P. The trimethylammonium headgroup of choline is a major determinant for substrate binding and specificity in choline oxidase. Arch. Biochem. Biophys. 430 (2004) 264-273. [PMID: 15369826]
5. Fan, F. and Gadda, G. On the catalytic mechanism of choline oxidase. J. Am. Chem. Soc. 127 (2005) 2067-2074. [PMID: 15713082]
6. Waditee, R., Tanaka, Y., Aoki, K., Hibino, T., Jikuya, H., Takano, J., Takabe, T. and Takabe, T. Isolation and functional characterization of N-methyltransferases that catalyze betaine synthesis from glycine in a halotolerant photosynthetic organism Aphanothece halophytica. J. Biol. Chem. 278 (2003) 4932-4942. [PMID: 12466265]
7. Fan, F., Ghanem, M. and Gadda, G. Cloning, sequence analysis, and purification of choline oxidase from Arthrobacter globiformis: a bacterial enzyme involved in osmotic stress tolerance. Arch. Biochem. Biophys. 421 (2004) 149-158. [PMID: 14678796]
8. Gadda, G. Kinetic mechanism of choline oxidase from Arthrobacter globiformis. Biochim. Biophys. Acta 1646 (2003) 112-118. [PMID: 12637017]