Reaction: choline + O2 + 2 reduced ferredoxin + 2 H+ = betaine aldehyde hydrate + H2O + 2 oxidized ferredoxin
Glossary: betaine = glycine betaine = N,N,N-trimethylammonioacetate
betaine aldehyde = N,N,N-trimethyl-2-oxoethylammonium
choline = (2-hydroxyethyl)trimethylammonium
Systematic name: choline,reduced-ferredoxin:oxygen oxidoreductase
Comments: The spinach enzyme, which is located in the chloroplast, contains a Rieske-type [2Fe-2S] cluster, and probably also a mononuclear Fe centre. Requires Mg2+. Catalyses the first step of glycine betaine synthesis. In many bacteria, plants and animals, betaine is synthesized in two steps: (1) choline to betaine aldehyde and (2) betaine aldehyde to betaine. Different enzymes are involved in the first reaction. In plants, the reaction is catalysed by this enzyme whereas in animals and many bacteria it is catalysed by either membrane-bound EC 188.8.131.52 (choline dehydrogenase) or soluble EC 184.108.40.206 (choline oxidase) . The enzyme involved in the second step, EC 220.127.116.11 (betaine-aldehyde dehydrogenase), appears to be the same in plants, animals and bacteria. In some bacteria, betaine is synthesized from glycine through the actions of EC 18.104.22.168 (glycine/sarcosine N-methyltransferase) and EC 22.214.171.124 (sarcosine/dimethylglycine N-methyltransferase).
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number: 118390-76-4
1. Brouquisse, R., Weigel, P., Rhodes, D., Yocum, C.F. and Hanson, A.D. Evidence for a ferredoxin-dependent choline monooxygenase from spinach chloroplast stroma. Plant Physiol. 90 (1989) 322-329. [PMID: 16666757]
2. Burnet, M., Lafontaine, P.J. and Hanson, A.D. Assay, purification, and partial characterization of choline monooxygenase from spinach. Plant Physiol. 108 (1995) 581-588. [PMID: 12228495]
3. Rathinasabapathi, B., Burnet, M., Russell, B.L., Gage, D.A., Liao, P., Nye, G.J., Scott, P., Golbeck, J.H. and Hanson, A.D. Choline monooxygenase, an unusual iron-sulfur enzyme catalyzing the first step of glycine betaine synthesis in plants: Prosthetic group characterization and cDNA cloning. Proc. Natl. Acad. Sci. USA 94 (1997) 3454-3458. [PMID: 9096415]
4. Russell, B.L., Rathinasabapathi, B. and Hanson, A.D. Osmotic stress induces expression of choline monooxygenase in sugar beet and amaranth. Plant Physiol. 116 (1998) 859-865. [PMID: 9489025]
5. Nuccio, M.L., Russell, B.L., Nolte, K.D., Rathinasabapathi, B., Gage, D.A. and Hanson, A.D. Glycine betaine synthesis in transgenic tobacco expressing choline monooxygenase is limited by the endogenous choline supply. Plant J. 16 (1998) 101-110.
6. Nuccio, M.L., Russell, B.L., Nolte, K.D., Rathinasabapathi, B., Gage, D.A. and Hanson, A.D. The endogenous choline supply limits glycine betaine synthesis in transgenic tobacco expressing choline. Plant J. 16 (1998) 487-496. [PMID: 9881168]
7. 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]