Acetyl-CoA synthetase from the amitochondriate eukaryote Giardia lamblia belongs to the newly recognized superfamily of acyl-CoA synthetases (nucleoside diphosphate-forming)

The gene coding for the acetyl-CoA. synthetase (ADP-forming) from the amito chondriate eukaryote Giardia lamblia has been expressed in Escherichia coli . The recombinant enzyme exhibited the same substrate specificity as the na tive enzyme, utilizing acetyl-CoA and adenine nucleotides as preferred subs trates and less efficiently, propionyl- and succinyl-CoA. N- and C-terminal parts of the G. lamblia acetyl-CoA sythetase sequence were found to be hom ologous to the alpha- and beta-subunits, respectively, of succinyl-CoA synt hetase, Sequence analysis of homologous enzymes from various bacteria archa ea, and the eukaryote, Plasmodium fad ciparum, identified conserved feature s in their organization, which allowed us to delineate a new superfamily of acyl-CoA synthetases (nucleoside diphosphate-forming) and its signature mo tifs, The representatives of this new superfamily of thiokinases vary in th eir domain arrangement, some consisting of separate alpha- and beta-subunit s and others comprising fusion proteins in alpha-beta or beta-alpha orienta tion. The presence of homologs of acetyl synthetase (ADP-forming) in such h uman pathogens as G. lamblia, Yersinia pestis, Bordetella pertussis, Pseudo monas aeruginosa, Vibrio cholerae, Salmonella typhi, Porphyromonas gingival is, and the malaria agent P. falciparum suggests that they might be used as potential drug targets.