3had
BIOCHEMICAL CHARACTERIZATION AND STRUCTURE DETERMINATION OF HUMAN HEART SHORT CHAIN L-3-HYDROXYACYL COA DEHYDROGENASE PROVIDE INSIGHT INTO CATALYTIC MECHANISM
Structural highlights
DiseaseHCDH_HUMAN Defects in HADH are the cause of 3-alpha-hydroxyacyl-CoA dehydrogenase deficiency (HADH deficiency) [MIM:231530. HADH deficiency is a metabolic disorder with various clinical presentations including hypoglycemia, hepatoencephalopathy, myopathy or cardiomyopathy, and in some cases sudden death. Defects in HADH are the cause of familial hyperinsulinemic hypoglycemia type 4 (HHF4) [MIM:609975; also known as persistent hyperinsulinemic hypoglycemia of infancy (PHHI) or congenital hyperinsulinism. HHF is the most common cause of persistent hypoglycemia in infancy and is due to defective negative feedback regulation of insulin secretion by low glucose levels. It causes nesidioblastosis, a diffuse abnormality of the pancreas in which there is extensive, often disorganized formation of new islets. Unless early and aggressive intervention is undertaken, brain damage from recurrent episodes of hypoglycemia may occur. HHF4 should be easily recognizable by analysis of acylcarnitine species and that this disorder responds well to treatment with diazoxide. It provides the first 'experiment of nature' that links impaired fatty acid oxidation to hyperinsulinism and that provides support for the concept that a lipid signaling pathway is implicated in the control of insulin secretion.[1] FunctionHCDH_HUMAN Plays an essential role in the mitochondrial beta-oxidation of short chain fatty acids. Exerts it highest activity toward 3-hydroxybutyryl-CoA. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedHuman heart short chain L-3-hydroxyacyl-CoA dehydrogenase (SCHAD) catalyzes the oxidation of the hydroxyl group of L-3-hydroxyacyl-CoA to a keto group, concomitant with the reduction of NAD+ to NADH, as part of the beta-oxidation pathway. The homodimeric enzyme has been overexpressed in Escherichia coli, purified to homogeneity, and studied using biochemical and crystallographic techniques. The dissociation constants of NAD+ and NADH have been determined over a broad pH range and indicate that SCHAD binds reduced cofactor preferentially. Examination of apparent catalytic constants reveals that SCHAD displays optimal enzymatic activity near neutral pH, with catalytic efficiency diminishing rapidly toward pH extremes. The crystal structure of SCHAD complexed with NAD+ has been solved using multiwavelength anomalous diffraction techniques and a selenomethionine-substituted analogue of the enzyme. The subunit structure is comprised of two domains. The first domain is similar to other alpha/beta dinucleotide folds but includes an unusual helix-turn-helix motif which extends from the central beta-sheet. The second, or C-terminal, domain is primarily alpha-helical and mediates subunit dimerization and, presumably, L-3-hydroxyacyl-CoA binding. Molecular modeling studies in which L-3-hydroxybutyryl-CoA was docked into the enzyme-NAD+ complex suggest that His 158 serves as a general base, abstracting a proton from the 3-OH group of the substrate. Furthermore, the ability of His 158 to perform such a function may be enhanced by an electrostatic interaction with Glu 170, consistent with previous biochemical observations. These studies provide further understanding of the molecular basis of several inherited metabolic disease states correlated with L-3-hydroxyacyl-CoA dehydrogenase deficiencies. Biochemical characterization and crystal structure determination of human heart short chain L-3-hydroxyacyl-CoA dehydrogenase provide insights into catalytic mechanism.,Barycki JJ, O'Brien LK, Bratt JM, Zhang R, Sanishvili R, Strauss AW, Banaszak LJ Biochemistry. 1999 May 4;38(18):5786-98. PMID:10231530[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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