. "In many bacteria, plants and animals, the osmoprotectant betaine is synthesized using different enzymes to catalyze the conversion of (1) choline into betaine aldehyde and (2) betaine aldehyde into betaine." . "The enzyme involved in the second step, EC 1.2.1.8, appears to be the same in plants, animals and bacteria." . "In plants, the first reaction is catalyzed by EC 1.14.15.7 whereas in animals and many bacteria, it is catalyzed by either EC 1.1.99.1 or EC 1.1.3.17." . . . "Choline dehydrogenase" . "Choline oxidase" . "Choline-cytochrome c reductase" . "Choline + acceptor = betaine aldehyde + reduced acceptor." . "Pyrroloquinoline quinone" .