Involved in the biosynthesis of the osmoprotectant glycine betaine. Catalyzes the oxidation of choline to betaine aldehyde and betaine aldehyde to glycine betaine at the same rate. A + choline = AH2 + betaine aldehyde betaine aldehyde + H2O + NAD(+) = glycine betaine + 2 H(+) + NADH Activated by high osmotic strength. Optimum pH is 7.5 for choline dehydrogenase and is between 7.5 and 9.5 for glycine betaine-aldehyde dehydrogenase. Amine and polyamine biosynthesis; betaine biosynthesis via choline pathway; betaine aldehyde from choline (cytochrome c reductase route): step 1/1. By osmotic stress. Choline is required for full expression. Oxygen and choline exert their control via the transacting DNA-binding proteins ArcA and BetI, respectively. Cells lacking this gene do not grow at high osmotic strength in the presence of choline, but are able to grow when the medium is supplemented with glycine betaine. Belongs to the GMC oxidoreductase family. Truncated N-terminus.