TY - JOUR
T1 - Branched-chain alpha-keto acid catabolism via the gene products of the bkd operon in Enterococcus faecalis: a ne, secreted metabolite serving as a temporary redox sink.
AU - Ward, D.E.
AU - van der Weijden, C.C.
AU - van der Merwe, M.J.
AU - Westerhoff, H.V.
AU - Claiborne, A.
AU - Snoep, J.L.
PY - 2000
Y1 - 2000
N2 - Recently the bkd gene cluster from Enterococcus faecalis was sequenced, and it was shown that the gene products constitute a pathway for the catabolism of branched-chain α-keto acids. We have now investigated the regulation and physiological role of this pathway. Primer extension analysis identified the presence of a single promoter upstream of the bkd gene cluster. Furthermore, a putative catabolite-responsive element was identified in the promoter region, indicative of catabolite repression. Consistent with this was the observation that expression of the bkd gene cluster is repressed in the presence of glucose, fructose, and lactose. It is proposed that the conversion of the branched-chain α-keto acids to the corresponding free acids results in the formation of ATP via substrate level phosphorylation. The utilization of the α-keto acids resulted in a marked increase of biomass, equivalent to a net production of 0.5 mol of ATP per mol of α-keto acid metabolized. The pathway was active under aerobic as well as anaerobic conditions. However, under anaerobic conditions the presence of a suitable electron acceptor to regenerate NAD
AB - Recently the bkd gene cluster from Enterococcus faecalis was sequenced, and it was shown that the gene products constitute a pathway for the catabolism of branched-chain α-keto acids. We have now investigated the regulation and physiological role of this pathway. Primer extension analysis identified the presence of a single promoter upstream of the bkd gene cluster. Furthermore, a putative catabolite-responsive element was identified in the promoter region, indicative of catabolite repression. Consistent with this was the observation that expression of the bkd gene cluster is repressed in the presence of glucose, fructose, and lactose. It is proposed that the conversion of the branched-chain α-keto acids to the corresponding free acids results in the formation of ATP via substrate level phosphorylation. The utilization of the α-keto acids resulted in a marked increase of biomass, equivalent to a net production of 0.5 mol of ATP per mol of α-keto acid metabolized. The pathway was active under aerobic as well as anaerobic conditions. However, under anaerobic conditions the presence of a suitable electron acceptor to regenerate NAD
U2 - 10.1128/JB.182.11.3239-3246.2000
DO - 10.1128/JB.182.11.3239-3246.2000
M3 - Article
SN - 0021-9193
VL - 182
SP - 3239
EP - 3246
JO - Journal of Bacteriology
JF - Journal of Bacteriology
ER -