In enzymology, glutarate-semialdehyde dehydrogenase () is an enzyme that catalyzes the chemical reaction
The three substrates of this enzyme are 5-oxopentanoic acid (glutarate semialdehyde), oxidised nicotinamide adenine dinucleotide (NAD<sup>+</sup>), and water. Its products are glutaric 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 glutarate-semialdehyde:NAD+ oxidoreductase. This enzyme is also called glutarate semialdehyde dehydrogenase. This enzyme participates in lysine degradation.