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 18.104.22.168 (choline dehydrogenase) or soluble EC 22.214.171.124 (choline oxidase) . The enzyme involved in the second step, EC 126.96.36.199 (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 188.8.131.52 (glycine/sarcosine N-methyltransferase) and EC 184.108.40.206 (sarcosine/dimethylglycine N-methyltransferase).
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number: 118390-76-4
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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]