Multiple Regulators Control Expression of the Entner-Doudoroff Aldolase (Eda) of Escherichia coli

Abstract

The Escherichia coli eda gene, which encodes the Entner-Doudoroff aldolase, is central to the catabolism of several sugar acids. Here, we show that Eda synthesis is induced by growth on gluconate, glucuronate, or methyl-␤-D-glucuronide; phosphate limitation; and carbon starvation. Transcription of eda initiates from three promoters, designated P1, P2, and P4, each of which is responsible for induction under different growth conditions. P1 controls eda induction on gluconate and is regulated by GntR. P2 controls eda induction on glucuronate and galacturonate and is regulated by KdgR. P4 is active under conditions of phosphate starvation and is directly controlled by PhoB. In addition, CsrA activates Eda synthesis, apparently by an indirect mechanism that may be involved in the modest changes in expression level that are associated with carbon starvation. The complex regulation of eda is discussed with respect to its several physiological roles, which apparently accommodate not only sugar acid catabolism but also detoxification of metabolites that could accumulate during starvation-induced stress.Sugar acids are metabolized via the Entner-Doudoroff and Ashwell pathways (1,5,8,20). The Entner-Doudoroff aldolase, encoded by the eda gene, is necessary for growth on several mucus-derived sugar acids (20), which may define a niche for Escherichia coli colonization of the mammalian large intestine (4). Mutants lacking the key enzyme of the Entner-Doudoroff pathway, 6-phosphogluconate dehydratase (encoded by edd), are compromised in their ability to colonize the mouse intestine (4), as are eda mutants (29).Eda cleavage of 2-keto-3-deoxy-6-phosphogluconate (KDPG) to pyruvate and triose-3-phosphate is a common step of hexonate and hexuronate catabolism (20). Eda has also been found to have a role in the degradation of 2-keto-4-hydroxyglutarate (KHG) to pyruvate and glyoxylate (16). Although this reaction has not been shown to occur in vivo, cleavage of KHG could serve in tricarboxylic acid (TCA) cycle regulation or, when operating in the reverse direction, in the detoxification of glyoxylate. Cloning and sequencing the genes encoding these functions revealed that KHG aldolase and Eda are the same enzyme (7, 18). However, this study is the first to extensively characterize eda regulation.The eda gene is located immediately downstream of edd, at 40.5 min on the E. coli chromosome (Fig. 1) (6). Previously, primer extension analysis of the eda regulatory region revealed four putative eda promoters (7). P1 drives cotranscription of edd and eda and is induced by growth on gluconate (7); P1 appears to be controlled by GntR (20,21,24), although binding of GntR to the P1 regulatory region was not established prior to this work. A second promoter, P2, is located within the terminal one-third of the edd coding sequence, and the closely spaced third and fourth putative promoters (P3 and P4) are located at the distal end of the edd coding region (7). High basal expression is characteristic of eda (20). Although it is known that the P2,...

A Set of Activators and Repressors Control Peripheral Glucose Pathways in Pseudomonas putida To Yield a Common Central Intermediate

“…We identified the same 14-bp dyad element (5Ј-TGAAACCGGTTTCA-3Ј) within the 35 nucleotides 5Ј upstream from each of the promoter start sites and suggest that this motif is also the target of PtxS in P. putida. In Pseudomonas putida, the direct phosphorylation of gluconate to 6PG is of minor importance in metabolic terms, which contrasts with the situation in other gram-negative (8,22,25,27,37) and gram-positive (Corynebacterium glutamicum [15] or Bacillus subtilis [43]) bacteria. However, the basic mode of regulation of gluconate metabolism in P. putida is similar to that in other bacteria.…”

“…It should be noted that pgl is under the control of HexR (Table 3) and GnuR (Table 2), which indicates that the gene can be controlled from the zwf-1 promoter under HexR control and from its own (as yet unidentified) promoter under GnuR control. This is somewhat surprising, but it may be related to the need to induce pgl and eda for the efficient catabolism of gluconate/2KG when these chemicals are used as the sole C source, as is also the case in P. fluorescens (27) and in Escherichia coli (8,22).…”

Identification of a Target Gene and Activating Stimulus for the YpdA/YpdB Histidine Kinase/Response Regulator System in Escherichia coli

“…Under conditions of overflow metabolism, pyruvate, like acetate, is a major component of the exometabolome in a broad range of bacteria (44). Sugar acids, e.g., gluconate or glucuronate, are predominantly metabolized via the Entner-Doudoroff pathway in E. coli, resulting in the production of 2 pyruvates per sugar acid (45). Pyruvate is a precursor of several compounds and a central metabolite; therefore, its cellular concentration has to be tightly controlled (46).…”

Circuitry Linking the Catabolite Repression and Csr Global Regulatory Systems of Escherichia coli

“…CsrA regulates the expression of genes involved in lifestyle transitions. In Escherichia coli, CsrA activates glycolysis and central carbon pathways (7)(8)(9)(10)(11)(12)(13) and motility (14,15). Conversely, it represses gluconeogenesis (7), glycogen biosynthesis (16)(17)(18)(19)(20), biofilm formation (21)(22)(23)(24), the stringent response (25), and expression of genes involved in other stress resistance and stationary-phase processes, e.g., cstA, hfq, cel, sdiA, and nhaR (24,(26)(27)(28)(29)(30).…”