ISSN:
1432-072X
Keywords:
ATP-citrate lyase
;
Citric acid cycle
;
Acetate oxidation
;
ATP synthesis via substrate level phosphorylation
;
Sulfate-reducing bacteria
;
Desulfobacter postgatei
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Desulfobacter postgatei is an acetate-oxidizing, sulfate-reducing bacterium that metabolizes acetate via the citric acid cycle. The organism has been reported to contain a si-citrate synthase (EC 4.1.3.7) which is activated by AMP and inorganic phosphate. It is show now, that the enzyme mediating citrate formation is an ATP-citrate lyase (EC 4.1.3.8) rather than a citrate synthase. Cell extracts (160,000xg supernatant) catalyzed the conversion of oxaloacetate (apparent K m=0.2 mM), acetyl-CoA (app. K m=0.1 mM), ADP (app. K m=0.06 mM) and phosphate (app. K m=0.7 mM) to citrate, CoA and ATP with a specific activity of 0.3 μmol·min-1·mg-1 protein. Per mol citrate formed 1 mol of ATP was generated. Cleavage of citrate (app. K m=0.05 mM; V max=1.2 μmol · min-1 · mg-1 protein) was dependent on ATP (app. K m=0.4 mM) and CoA (app. K m=0.05 mM) and yielded oxaloacetate, acetyl-CoA, ADP, and phosphate as products in a stoichiometry of citrate:CoA:oxaloacetate:ADP=1:1:1:1. The use of an ATP-citrate lyase in the citric acid cycle enables D. postgatei to couple the oxidation of acetate to 2 CO2 with the net synthesis of ATP via substrate level phosphorylation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00414812
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