Dehydrogenase innvolved in glycine betaine biosynthesis (PubMed:2320587, PubMed:24884441, PubMed:22345508). Metabolizes and detoxifies aldehyde products of polyamine degradation to non-toxic amino acids (Probable). Catalyzes the oxidation of betaine aldehyde to glycine betaine (PubMed:24884441, PubMed:22345508). Catalyzes the oxidation of 4-aminobutanal and 3-aminopropanal to 4-aminobutanoate and beta-alanine, respectively (PubMed:22345508). 4-aminobutanal + H2O + NAD(+) = 4-aminobutanoate + 2 H(+) + NADH 3-aminopropanal + H2O + NAD(+) = beta-alanine + 2 H(+) + NADH 4-(trimethylamino)butanal + H2O + NAD(+) = 4-(trimethylamino)butanoate + 2 H(+) + NADH betaine aldehyde + H2O + NAD(+) = glycine betaine + 2 H(+) + NADH Is reversibly and partially inactivated by betaine aldehyde in the absence of NAD(+) in a time- and concentration-dependent mode. Amine and polyamine biosynthesis; betaine biosynthesis via choline pathway; betaine from betaine aldehyde: step 1/1. Forms homodimers. Induced by salt stress. The catalytic activity of the dimeric betaine aldehyde (BADH) from spinach does not require potassium ion as cofactor, contrary to the tetrameric BADH from Pseudomonas aeruginosa (AC Q9HTJ1), although both enzymes contain potassium-binding sites. Belongs to the aldehyde dehydrogenase family.