Converts gamma-trimethylaminobutyraldehyde into gamma-butyrobetaine with high efficiency (in vitro). Can catalyze the irreversible oxidation of a broad range of aldehydes to the corresponding acids in an NAD-dependent reaction, but with low efficiency. 4-(trimethylamino)butanal + H2O + NAD(+) = 4-(trimethylamino)butanoate + 2 H(+) + NADH an aldehyde + H2O + NAD(+) = a carboxylate + 2 H(+) + NADH 4-aminobutanal + H2O + NAD(+) = 4-aminobutanoate + 2 H(+) + NADH Optimum pH is about 9.4 with propionaldehyde as substrate, and 7.5 with 4-aminobutyraldehyde as substrate. Amine and polyamine biosynthesis; carnitine biosynthesis. Homotetramer. Detected in brain (at protein level) (PubMed:8645224). High expression in adult liver, skeletal muscle, and kidney. Low levels in heart, pancreas, lung and brain (PubMed:8786138). Expressed in all regions of the brain. Expression levels are variable in the different brain areas, with the highest levels in the spinal cord and the lowest in the occipital pole. Strongly expressed in human embryonic brain (gestational age 12 weeks). Produced by alternative splicing. Produced by alternative initiation. Contains a predicted signal peptide at positions 1-24. Belongs to the aldehyde dehydrogenase family.