Catabolism of Hexuronides, Hexuronates, Aldonates, and Aldarates

Abstract

Following elucidation of the regulation of the lactose operon in Escherichia coli, studies on the metabolism of many sugars were initiated in the early 1960s. The catabolic pathways of D-gluconate and of the two hexuronates, D-glucuronate and D-galacturonate, were investigated. The post genomic era has renewed interest in the study of these sugar acids and allowed the complete characterization of the D-gluconate pathway and the discovery of the catabolic pathways for L-idonate, D-glucarate, galactarate, and ketogluconates. Among the various sugar acids that are utilized as sole carbon and energy sources to support growth of E. coli, galacturonate, glucuronate, and gluconate were shown to play an important role in the colonization of the mammalian large intestine. In the case of sugar acid degradation, the regulators often mediate negative control and are inactivated by interaction with a specific inducer, which is either the substrate or an intermediate of the catabolism. These regulators coordinate the synthesis of all the proteins involved in the same pathway and, in some cases, exert crosspathway control between related catabolic pathways. This is particularly well illustrated in the case of hexuronide and hexuronate catabolism. The structural genes encoding the different steps of hexuronate catabolism were identified by analysis of numerous mutants affected for growth with galacturonate or glucuronate. E. coli is able to use the diacid sugars D-glucarate and galactarate (an achiral compound) as sole carbon source for growth. Pyruvate and 2-phosphoglycerate are the final products of the D-glucarate/galactarate catabolism.

Oxygen limitation modulates pH regulation of catabolism and hydrogenases, multidrug transporters, and envelope composition in Escherichia coli K-12

“…Fermentation of sugar alcohols [ 57 ] and sugar acids [ 58 ] may cause less acidification than does glucose fermentation. It was proposed that the pH-dependent selection of sugar substrates may be correlated with their relative degree of acidification of the growth medium.…”

Molecular and Functional Insights into the Regulation of d -Galactonate Metabolism by the Transcriptional Regulator DgoR in Escherichia coli

“…E. coli degrades sugar acids via the Entner-Doudoroff or Ashwell pathway into glyceraldehyde 3-phosphate and pyruvate, which further enter the central metabolism through glycolysis and the tricarboxylic acid cycle, respectively (3,8). The sugar acid metabolic pathways are regulated by specific transcriptional regulators whose DNA-binding properties are influenced by binding to effectors, which could be either the sugar acid itself, its catabolic intermediate, or both (1,(9)(10)(11). D-Galactonate, a hexonate sugar acid, was first reported as a carbon source for E. coli in studies conducted in the 1970s (12).…”

Functional Microbial Responses to Alcohol Abstinence in Patients With Alcohol Use Disorder

“…During the superpathway of β-D-glucuronosides degradation process, β-glucuronosides undergo hydrolysis by β-glucuronidase to yield D-glucuronate. Similarly to the superpathway of β-D-glucuronosides degradation, β-glucuronidase is also the first enzyme utilized in the degradation of hexuronide and hexuronate (Mandrand-Berthelot et al, 2004). Besides, L-isoleucine biosynthesis II was increased in the CAP High patients at WEEK 3 compared with WEEK 1.…”