Involved in the biosynthesis of the osmoprotectant glycine betaine. Catalyzes the irreversible oxidation of betaine aldehyde to the corresponding acid. It is highly specific for betaine and has a significantly higher affinity for NAD than for NADP. betaine aldehyde + H2O + NAD(+) = glycine betaine + 2 H(+) + NADH betaine aldehyde + H2O + NADP(+) = glycine betaine + 2 H(+) + NADPH Binds 2 potassium ions per subunit. Aldehydes with apolar groups are the most effective inhibitors. N-Methylated compounds are also inhibitory, but to a much lesser degree than the aldehydes. The alcohols are more inhibitory than the corresponding acids, and the inhibitory effect increases with the degree of methylation from ethanolamine to choline. Optimum pH is between 7.5 and 9.5. Amine and polyamine biosynthesis; betaine biosynthesis via choline pathway; betaine from betaine aldehyde: step 1/1. Dimer of dimers. 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. Belongs to the aldehyde dehydrogenase family. Extended N-terminus. Extended N-terminus.