Succinate-semialdehyde dehydrogenase (NAD(P)+)

Succinate-semialdehyde dehydrogenase (NAD(P)+) is an enzyme (EC 1.2.1.16) belonging to the oxidoreductase family. It catalyzes the reversible oxidation of succinate semialdehyde to succinate, utilizing either NAD+ or NADP+ as a cofactor. The reaction proceeds as follows:

succinate semialdehyde + NAD(P)+ + H2O <-> succinate + NAD(P)H + H+

This enzyme plays a critical role in several metabolic pathways, including the catabolism of gamma-aminobutyric acid (GABA) and the lysine degradation pathway. In the GABA shunt, succinate-semialdehyde dehydrogenase converts succinate semialdehyde, a product of GABA transamination, into succinate, which can then enter the citric acid cycle (Krebs cycle).

Deficiencies in succinate-semialdehyde dehydrogenase activity in humans lead to succinic semialdehyde dehydrogenase deficiency (SSADHD), a rare autosomal recessive metabolic disorder characterized by the accumulation of succinate semialdehyde, GABA, and related compounds in bodily fluids. This accumulation can result in a variety of neurological and developmental problems, including intellectual disability, speech delay, ataxia, and behavioral abnormalities.

The enzyme's structure varies depending on the organism, but it generally comprises subunits containing a binding site for succinate semialdehyde and a binding site for NAD(P)+. The catalytic mechanism involves the transfer of hydride from succinate semialdehyde to NAD(P)+, resulting in the formation of succinate and NAD(P)H. Further research continues to explore the enzyme's specific structure, regulation, and role in various biological systems.