A Human Brain l-3-Hydroxyacyl-coenzyme A Dehydrogenase Is Identical to an Amyloid β-Peptide-binding Protein Involved in Alzheimer's Disease

Abstract

A novel L-3-hydroxyacyl-CoA dehydrogenase from human brain has been cloned, expressed, purified, and characterized. This enzyme is a homotetramer with a molecular mass of 108 kDa. Its subunit consists of 261 amino acid residues and has structural features characteristic of short chain dehydrogenases. It was found that the amino acid sequence of this human brain enzyme is identical to that of an endoplasmic reticulum amyloid ␤-peptide-binding protein (ERAB), which mediates neurotoxicity in Alzheimer's disease (Yan, S. D., Fu, J., Soto, C., Chen, X., Zhu, H., Al-Mohanna, F., Collison, K., Zhu, A., Stern, E., Saido, T., Tohyama, M., Ogawa, S., Roher, A., and Stern, D. (1997) Nature 389, 689 -695). The purification of human brain short chain L-3-hydroxyacyl-CoA dehydrogenase made it possible to characterize the structural and catalytic properties of ERAB. This NAD ؉ -dependent dehydrogenase catalyzes the reversible oxidation of L-3-hydroxyacyl-CoAs to form 3-ketoacyl-CoAs, but it does not act on the D-isomers. The catalytic rate constant of the purified enzyme was estimated to be 37 s ؊1 with apparent K m values of 89 and 20 M for acetoacetyl-CoA and NADH, respectively. The activity ratio of this enzyme for substrates with chain lengths of C 4 , C 8 , and C 16 was ϳ1:2:2. The human short chain L-3-hydroxyacyl-CoA dehydrogenase gene is organized into six exons and five introns and maps to chromosome Xp11.2. The amino-terminal NAD-binding region of the dehydrogenase is encoded by the first three exons, whereas the other exons code for the carboxyl-terminal substratebinding region harboring putative catalytic residues. The results of this study lead to the conclusion that ERAB involved in neuronal dysfunction is encoded by the human short chain L-3-hydroxyacyl-CoA dehydrogenase gene.L-3-Hydroxyacyl-CoA dehydrogenase (EC 1.1.1.35) catalyzes the third step of the fatty acid ␤-oxidation pathway: L-3-hydroxyacyl-CoA ϩ NAD ϩ i 3-ketoacyl-CoA ϩ NADH ϩ H ϩ (1). This reaction is known to be catalyzed by mitochondrial monofunctional L-3-hydroxyacyl-CoA dehydrogenase and by prokaryotic and eukaryotic multifunctional ␤-oxidation enzymes that possess an L-3-hydroxyacyl-CoA dehydrogenase functional domain (2, 3). The catalytic residue of this kind of dehydrogenase was recently identified to be a conserved histidine (4), and a conserved glutamate residue is also required for high catalytic efficiency (5). The catalytic residue of L-3-hydroxyacyl-CoA dehydrogenase was proposed to interact with the conserved glutamate, and this electrostatic interaction seemed to be strengthened by the binding of substrate (5). However, we were surprised to see that a catalytic His-Glu pair is not present in the newly isolated bovine liver type II dehydrogenase (6, 7), which is not homologous to any of the known L-3-hydroxyacylCoA dehydrogenases. More interestingly, it was reported that this new type of L-3-hydroxyacyl-CoA dehydrogenase was not found in human liver by either Northern blot or immunoblot analysis (6, 7). As a result, several important q...

Mental retardation linked to mutations in the HSD17B10 gene interfering with neurosteroid and isoleucine metabolism

“…This enzyme may have an additional role in neuropathology. When HSD10, also known as hydroxyacyl-CoA dehydrogenase (8,20), was bound to amyloid-␤ peptide, its enzymatic activity was shown to be slightly inhibited (37). However, we do not know whether amyloid-␤ peptide has a part to play in HSD10 deficiency because no neuropathological data for this inherited metabolic disorder is available.…”

“…The mutations c.419CϾT and c.776GϾC are respectively located in exons 4 and 6 of the HSD17B10 gene (11,20). Because the mutant proteins, Data deposition: The G/C transversion has been submitted to the dbSNP of NCBI, http:// www.ncbi.nlm.nih.gov/ (accession no.…”

“…The plasmid pSBET-HBHAD (20) was linearized by digestion with NdeI and EcoO109I. Oligomers 6HISF and 6HISR2 were annealed together and the resulting double-stranded DNA was subcloned into the NdeI-EcoO109I site of pSBET-HBHAD to generate pSBET6ϫHis-HSD10.…”

A novelHSD17B10mutation impairing the activities of the mitochondrial RNase P complex causes X-linked intractable epilepsy and neurodevelopmental regression

“…1,2 SDR5C1 is the only hydroxysteroid dehydrogenase (HSD) family member localized to mitochondria. [3][4][5][6][7][8] It acts by oxidoreduction of L-2-methyl-3-hydroxybutyryl-CoA at the penultimate step in the b-oxidation of isoleucine.…”

Sequestration of the active site by interdomain shifting: crystallographic and spectroscopic evidence for distinct conformations of L-3-Hydroxyacyl-CoA dehydrogenase

“…Mitochondrial trifunctional protein is a membraneassociated multi-functional enzyme which catalyzes three successive reactions of the β-oxidation spiral; sequence analysis of this enzyme reveals that HAD homology resides within the α-L-3-hydroxyacyl-CoA substrates (5,10). Designated L-3-hydroxyacyl-CoA dehydrogenase type II, it has been demonstrated that this enzyme is also a hydroxysteroid dehydrogenase homologue which bears no significant sequence homology to HAD.…”