Involved in the biosynthesis of the osmoprotectant glycine betaine. Catalyzes the irreversible oxidation of betaine aldehyde to the corresponding acid. In P.aeruginosa this reaction is a compulsory step in the assimilation of carbon and nitrogen when bacteria are growing in choline or choline precursors. Can use NADP(+) with similar efficiency to NAD(+), a property that can be used by the bacterium to produce the NADPH needed to combat the oxidative stress imposed by the host defenses. betaine aldehyde + H2O + NAD(+) = glycine betaine + 2 H(+) + NADH betaine aldehyde + H2O + NADP(+) = glycine betaine + 2 H(+) + NADPH Binds 2 potassium ions per subunit. kcat is 261 sec(-1) for the NADP-dependent oxidation of betaine aldehyde. kcat is 276 sec(-1) for the NAD-dependent oxidation of betaine aldehyde. Amine and polyamine biosynthesis; betaine biosynthesis via choline pathway; betaine from betaine aldehyde: step 1/1. Dimer of dimers. Belongs to the aldehyde dehydrogenase family.