In enzymology, a 4-trimethylammoniobutyraldehyde dehydrogenase () is an enzyme that catalyzes the chemical reaction
The three substrates of this enzyme are 4-trimethylammoniobutanal, oxidised nicotinamide adenine dinucleotide (NAD<sup>+</sup>), and water. Its products are 4-trimethylammoniobutanoate, reduced NADH, and a proton.
This enzyme belongs to the family of oxidoreductases, specifically those acting on the aldehyde or oxo group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is 4-trimethylammoniobutanal:NAD+ 1-oxidoreductase. Other names in common use include 4-trimethylaminobutyraldehyde dehydrogenase, and 4-N-trimethylaminobutyraldehyde dehydrogenase. This enzyme participates in lysine degradation and carnitine biosynthesis.