In enzymology, gamma-guanidinobutyraldehyde dehydrogenase () is an enzyme that catalyzes the chemical reaction
The three substrates of this enzyme are 4-guanidinobutanal, oxidised nicotinamide adenine dinucleotide (NAD<sup>+</sup>), and water. Its products are 4-guanidinobutyric acid, 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-guanidinobutanal:NAD+ 1-oxidoreductase. Other names in common use include alpha-guanidinobutyraldehyde dehydrogenase, 4-guanidinobutyraldehyde dehydrogenase, and GBAL dehydrogenase. This enzyme participates in urea cycle and metabolism of amino groups.