2-Methyl-3-Hydroxybutyryl-CoA Dehydrogenase Deficiency Is Caused by Mutations in the HADH2 Gene

• DOI: 10.1086/375116
• Publication Date: 2003-04-23T16:55:30Z
• Authors: Rob Ofman; P.N. Jos Ruiter; Marike Feenstra; Marinus Duran; Tien Bwee Poll-The; Johannes Zschocke; Regina Ensenauer; Willy Lehnert; Jörn Oliver Sass; Wolfgang Sperl; J.A. Ronald Wanders
• Keywords: Male; 0301 basic medicine; X Chromosome; DNA Mutational Analysis; Molecular Sequence Data; Mutation, Missense; 3-Hydroxyacyl CoA Dehydrogenases; Pedigree; 3. Good health; Alcohol Oxidoreductases; 03 medical and health sciences; Amino Acid Substitution; Liver; Genetics; Animals; Humans; Genetics(clinical); Cattle; Female

2-methyl-3-hydroxybutyryl-CoA dehydrogenase (MHBD) deficiency is a novel inborn error of isoleucine degradation. In this article, we report the elucidation of the molecular basis of MHBD deficiency. To this end, we purified the enzyme from bovine liver. MALDI-TOF mass spectrometry analysis revealed that the purified protein was identical to bovine 3-hydroxyacyl-CoA dehydrogenase type II. The human homolog of this bovine enzyme is a short-chain 3-hydroxyacyl-CoA dehydrogenase, also known as the "endoplasmic reticulum-associated amyloid-beta binding protein" (ERAB). This led to the identification of the X-chromosomal gene involved, which previously had been denoted "HADH2." Sequence analysis of the HADH2 gene from patients with MHBD deficiency revealed the presence of two missense mutations (R130C and L122V). Heterologous expression of the mutant cDNAs in Escherichia coli showed that both mutations almost completely abolish enzyme activity. This confirms that MHBD deficiency is caused by mutations in the HADH2 gene.