In enzymology, succinate-semialdehyde dehydrogenase (SSADH) () is an enzyme that catalyzes the chemical reaction
The three substrates of this enzyme are succinic semialdehyde, oxidised nicotinamide adenine dinucleotide (NAD<sup>+</sup>), and water. Its products are succinic 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 succinate-semialdehyde:NAD+ oxidoreductase. Other names in common use include succinate semialdehyde dehydrogenase, succinic semialdehyde dehydrogenase, succinyl semialdehyde dehydrogenase, and succinate semialdehyde:NAD+ oxidoreductase. This enzyme participates in glutamate and butyrate metabolism.
Succinate-semialdehyde dehydrogenase is found in organisms ranging across the tree of life from bacteria to humans. It is important in the degradation of ó-aminobutyric acid in humans, and deficiency of the enzyme causes serious health effects (succinic semialdehyde dehydrogenase deficiency).
In bacteria, the enzyme is also involved in ó-aminobutyric acid degradation, but can be recruited to facilitate other functions, such as converting succinate-semialdehyde formed during fission of the pyridine ring to succinic acid for entry into the Krebs Cycle.