Identification of the gene encoding the activator of(R)‐2‐hydroxyglutaryl‐CoA dehydratase from Acidaminococcus fermentans by gene expression in Escherichia coli

( R )‐2‐Hydroxyglutaryl‐CoA dehydratase (HGDA/B) from Acidaminococcus fermentans requires an activator protein for activity. This activator (HGDC) has not yet been purified from its natural source due to its low concentration combined with an extreme sensitivity towards oxygen. Gene expression in Escherichia coli identified an open reading frame (780 bp) as the gene encoding HGDC. Dehydratase activity was stimulated at least tenfold by cell‐free extracts of E. coli cells transformed with a plasmid carrying hgdC . On the chromosome the hgdC gene is located just before hgdA and hgdB .