MOLECULAR ANALYSIS OF THE ANAEROBIC SUCCINATE DEGRADATION PATHWAY IN CLOSTRIDIUM-KLUYVERI

A region of genomic DNA from Clostridium kluyveri was cloned in Escher ichia coli by a screening strategy which was based on heterologous exp ression of the clostridial 4-hydroxybutyrate dehydrogenase gene. The g ene region (6,575 bp) contained several open reading frames which enco ded the coenzyme A (CoA)- and NADP(+)-dependent succinate-semialdehyde dehydrogenase (sncD), the 4-hydroxybutyrate dehydrogenase (4hbD), and a succinyl-CoA:CoA transferase (catl), as analyzed by heterologous ex pression in E. coli. An open reading frame encoding a putative membran e protein (orfY) and the 5' region of a gene encoding a sigma(54)-homo logous sigma factor (sigL) were identified as well. Transcription was investigated by Northern (RNA) blot analysis. Protein sequence compari sons of SucD and 4HbD revealed similarities to the adhE (aad) gene pro ducts from E. coli and Clostridium acetobutylicum and to enzymes of th e novel class (III) of alcohol dehydrogenases. A comparison of CoA-dep endent aldehyde dehydrogenases is presented.