CLONING AND CHARACTERIZATION OF HELICOBACTER-PYLORI SUCCINYL COA-ACETOACETATE COA-TRANSFERASE, A NOVEL PROKARYOTIC MEMBER OF THE COA-TRANSFERASE FAMILY

Sequencing of a fragment of Helicobacter pylori genome led to the iden tification of two open reading frames showing striking homology with C oenzyme A (CoA) transferases, enzymes catalyzing the reversible transf er of CoA from one carboxylic acid to another. The genes were present in all H. pylori strains tested by polymerase chain reaction or slot b lotting but not in Campylobacter jejuni. Genes for the putative A and B subunits of H. pylori CoA-transferase were introduced into the bacte rial expression vector pKK223-3 and expressed in Escherichia coli JM10 5 cells. Amino acid sequence comparisons, combined with measurements o f enzyme activities using different CoA donors and accepters, identifi ed the H. pylori CoA-transferase as a succinyl CoA:acetoacetate CoA-tr ansferase. This activity was consistently observed in different H. pyl ori strains, Antibodies raised against either recombinant A or B subun its recognized two distinct subunits of M-r similar to 26,000 and 24,0 00 that are both necessary for H. pylori CoA transferase function. The lack of alpha-ketoglutarate dehydrogenase and of succinyl CoA synthet ase activities indicates that the generation of succinyl CoA is not me diated by the tricarboxylic acid cycle in H. pylori. We postulate the existence of an alternative pathway where the CoA-transferase is essen tial for energy metabolism.