The crystal structure of human SSADH in complex with NAD+
[SSDH_HUMAN] Defects in ALDH5A1 are the cause of succinate semialdehyde dehydrogenase deficiency (SSADH deficiency) [MIM:271980]. SSADH deficiency is a rare inborn error in the metabolism of 4-aminobutyric acid (GABA) which leads to accumulation of 4-hydroxybutyric acid in physiologic fluids of patients. The disease is characterized by severe ataxia and by mildly retarded psychomotor development.
Publication Abstract from PubMed
Succinic semialdehyde dehydrogenase (SSADH) is involved in the final degradation step of the inhibitory neurotransmitter gamma-aminobutyric acid by converting succinic semialdehyde to succinic acid in the mitochondrial matrix. SSADH deficiency, a rare autosomal recessive disease, exhibits variable clinical phenotypes, including psychomotor retardation, language delay, behaviour disturbance and convulsions. Here, we present crystal structures of both the oxidized and reduced forms of human SSADH. Interestingly, the structures show that the catalytic loop of the enzyme undergoes large structural changes depending on the redox status of the environment, which is mediated by a reversible disulphide bond formation between a catalytic Cys340 and an adjacent Cys342 residues located on the loop. Subsequent in vivo and in vitro studies reveal that the 'dynamic catalytic loop' confers a response to reactive oxygen species and changes in redox status, indicating that the redox-switch modulation could be a physiological control mechanism of human SSADH. Structural basis for the substrate specificity of the enzyme and the impact of known missense point mutations associated with the disease pathogenesis are presented as well.
Redox-switch modulation of human SSADH by dynamic catalytic loop.,Kim YG, Lee S, Kwon OS, Park SY, Lee SJ, Park BJ, Kim KJ EMBO J. 2009 Apr 8;28(7):959-68. Epub 2009 Mar 19. PMID:19300440
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.