The EutQ and EutP proteins are novel acetate kinases involved in ethanolamine catabolism: physiological implications for the function of the ethanolamine metabolosome inSalmonella enterica

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Abstract

Salmonella entericacatabolizes ethanolamine inside a compartment known as the metabolosome. Theethanolamineutilization (eut) operon of this bacterium encodes all functions needed for the assembly and function of this structure. To date, the roles of EutQ and EutP were not known. Herein we show that both proteins have acetate kinase activity and that EutQ is required during anoxic growth ofS. entericaon ethanolamine and tetrathionate. EutP and EutQ-dependent ATP synthesis occurred when enzymes were incubated with ADP, Mg(II) ions and acetyl-phosphate. EutQ and EutP also synthesized acetyl-phosphate from ATP and acetate. Although EutP had acetate kinase activity, ΔeutPstrains lacked discernible phenotypes under the conditions where ΔeutQstrains displayed clear phenotypes. The kinetic parameters indicate that EutP is a faster enzyme than EutQ. Our evidence supports the conclusion that EutQ and EutP represent novel classes of acetate kinases. We propose that EutQ is necessary to drive flux through the pathway under physiological conditions, preventing a buildup of acetaldehyde. We also suggest that ATP generated by these enzymes may be used as a substrate for EutT, the ATP-dependent corrinoid adenosyltransferase and for the EutA ethanolamine ammonia-lyase reactivase.

The 17-geneeutoperon ofSalmonella entericasv. Typhimurium encodes functions needed for the catabolism of ethanolamine. The roles of all but three of the Eut proteins are known. We reportin vivoandin vitroevidence that EutP and EutQ are novel acetate kinases. Importantly, EutQ-deficient strains cannot respire ethanolamine to tetrathionate under anoxic conditions, a condition relevant to the pathogenic lifestyle of this bacterium.

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