Identification of an acetoacetyl coenzyme A synthetase-dependent pathway for utilization of L-(+)-3-hydroxybutyrate in Sinorhizobium meliloti.
D-(-)-3-Hydroxybutyrate (DHB), the immediate depolymerization product of the intracellular carbon store poly-3-hydroxybutyrate (PHB), is oxidized by the enzyme 3-hydroxybutyrate dehydrogenase to acetoacetate (AA) in the PHB degradation pathway. Externally supplied DHB can serve as a sole source of carbon and energy to support the growth of Sinorhizobium meliloti. In contrast, wild-type S. meliloti is not able to utilize the L-(+) isomer of 3-hydroxybutyrate (LHB) as a sole source of carbon and energy. In this study, we show that overexpression of the S. meliloti acsA2 gene, encoding acetoacetyl coenzyme A (acetoacetyl-CoA) synthetase, confers LHB utilization ability, and this is accompanied by novel LHB-CoA synthetase activity. Kinetics studies with the purified AcsA2 protein confirmed its ability to utilize both AA and LHB as substrates and showed that the affinity of the enzyme for LHB was clearly lower than that for AA. These results thus provide direct evidence for the LHB-CoA synthetase activity of the AcsA2 protein and demonstrate that the LHB utilization pathway in S. meliloti is AcsA2 dependent.
Aneja
Punita
P
Department of Natural Resource Sciences, McGill University, Ste-Anne-de-Bellevue, Quebec H9X 3V9, Canada.
Dziak
Renata
R
Cai
Guo-Qin
GQ
Charles
Trevor C
TC
D020155:3-Hydroxybutyric Acid / Q000378:metabolism*; D000090:Acetoacetates / Q000378:metabolism; D003066:Coenzyme A Ligases / Q000235:genetics / Q000378:metabolism*; D006885:Hydroxybutyrates / Q000378:metabolism*; D016254:Mutagenesis, Insertional; D011091:Polyesters / Q000378:metabolism*; D016962:Sinorhizobium meliloti / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D013379:Substrate Specificity; D000094122:Polyhydroxybutyrates
D020155:3-Hydroxybutyric Acid; D000090:Acetoacetates; D003066:Coenzyme A Ligases; D006885:Hydroxybutyrates; D011091:Polyesters; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates; C016635:acetoacetic acid; C023747:acetoacetyl-CoA synthetase