Acetate excretion during growth of Salmonella enterica on ethanolamine requires phosphotransacetylase (EutD) activity, and acetate recapture requires acetyl-CoA synthetase (Acs) and phosphotransacetylase (Pta) activities

Abstract

This report shows that Salmonella enterica catabolizes ethanolamine to acetyl-CoA (Ac-CoA), which enters the glyoxylate bypass and tricarboxylic acid cycle for the generation of energy and central metabolites. During growth on ethanolamine, S. enterica excreted acetate, whose recapture depended on Ac-CoA synthetase (Acs) and the housekeeping phosphotransacetylase (Pta) enzyme activities. The Pta enzyme did not play a role in acetate excretion during growth of S. enterica on ethanolamine. It is proposed that during growth on ethanolamine, acetate excretion is necessary to maintain a pool of free CoA. Acetate excretion requires the eut operon-encoded phosphotransacetylase (EutD) and acetate kinase (Ack) enzymes. EutD function was not required for growth on ethanolamine, and an eutD strain showed only a slight reduction in growth rate. The existence of an as-yet-unidentified system that releases acetate was revealed during growth of a strain lacking Acs, the housekeeping phosphotransacetylase (Pta), and EutD. The functions of pyruvate oxidase (PoxB), Ack and STM3118 protein [a homologue of the Saccharomyces cerevisiae Ac-CoA hydrolase (Ach1p) enzyme] were not involved in the release of acetate by the acs pta eutD strain.

EutR Is a Direct Regulator of Genes That Contribute to Metabolism and Virulence in Enterohemorrhagic Escherichia coli O157:H7

“…In EHEC and Salmonella, the genes that encode EA metabolism are located within the EA utilization (eut) operon. The eut operon includes 17 genes that allow transport and breakdown of EA, as well as production of a carboxysome-like structure that contains toxic breakdown products of EA metabolism (10)(11)(12)(13)(14)(15)(16)(17). The eut operon also encodes the transcriptional regulator EutR, which promotes expression of the eut operon in response to EA and vitamin B 12 (14,18).…”

Microbial Engineering for Aldehyde Synthesis

“…Some bacteria have naturally evolved solutions to aldehyde toxicity beyond rapid reduction of aldehydes, such as protein microcompartments that feature aldehyde intermediates (88,89). If control of selective metabolite transport through the protein shells were achieved, then the engineering of these compartments for biosynthesis of new aldehyde-derived products might aid in limiting the pool size of free aldehyde intermediates (90).…”

Bacterial Microcompartments

“…The analogous function of the EutBMCs would be to contain acetaldehyde until it is further metabolized to acetyl-CoA by acetaldehyde dehydrogenase (EutE (65)) in the BMC interior prior to entry into the central metabolism, or converted to acetyl-phosphate by a phosphotransacetylase (EutD (9, 64)) (10) (Figure 2c). An alternate branch of the pathway, presumed to be contained within the BMC as well, would convert acetaldehyde to ethanol through action of the putative alcohol dehydrogenase EutG (10,64) (Figure 2c). …”