Analysis of an <i>Erwinia chrysanthemi</i> gene cluster involved in pectin degradation

Condemine, Guy; Robert‐Baudouy, Janine

doi:10.1111/j.1365-2958.1991.tb02149.x

Cited by 52 publications

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“…In the Y. enterocolitica system, the YeKdgF-catalyzed generation of DKI would provide the substrate for downstream processing by the isomerase YeKduI and the NADH-dependent reductase YeKduD into KDG (5). To test this, we established a coupled assay in which the oxidation of NADH by YeKduD is linked to the sequential processing of digalacturonate by YeOgl, YeKdgF, and YeKduI (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…S1) (6). kdgF was initially identified within the pectin degradation locus of Dickeya dadantii (formerly Erwinia chrysanthemi) where it was observed to be regulated by the pectin degradation repressor protein KdgR (5). Although disruption of kdgF in D. dadantii did not prevent growth on polygalacturonate (PGA), it did result in lower induction of pectate lyases by PGA and reduced maceration of potato tubers.…”

mentioning

confidence: 99%

“…In pectinolytic organisms, the conversion of 4,5-unsaturated galacturonate (ΔGalUA) to KDG occurs via three steps and the two intermediates 5-keto-4-deoxyuronate (DKI) and 2,5-diketo-3-deoxygluconate (DKII). The final two steps are catalyzed by an isomerase (KduI) and a reductase (KduD) (5). In alginolytic organisms, 4,5-unsaturated mannuronate (ΔManUA) and guluronate (ΔGulUA) are converted to KDG via two steps and the intermediate 4-deoxy-L-erythro-5-hexoseulose uronate (DEH), with the second step catalyzed by DEH reductase (4) (Fig.…”

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KdgF, the missing link in the microbial metabolism of uronate sugars from pectin and alginate

Hobbs

Lee

Robb

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Uronates are charged sugars that form the basis of two abundant sources of biomass-pectin and alginate-found in the cell walls of terrestrial plants and marine algae, respectively. These polysaccharides represent an important source of carbon to those organisms with the machinery to degrade them. The microbial pathways of pectin and alginate metabolism are well studied and essentially parallel; in both cases, unsaturated monouronates are produced and processed into the key metabolite 2-keto-3-deoxygluconate (KDG). The enzymes required to catalyze each step have been identified within pectinolytic and alginolytic microbes; yet the function of a small ORF, kdgF, which cooccurs with the genes for these enzymes, is unknown. Here we show that KdgF catalyzes the conversion of pectin-and alginate-derived 4,5-unsaturated monouronates to linear ketonized forms, a step in uronate metabolism that was previously thought to occur spontaneously. Using enzyme assays, NMR, mutagenesis, and deletion of kdgF, we show that KdgF proteins from both pectinolytic and alginolytic bacteria catalyze the ketonization of unsaturated monouronates and contribute to efficient production of KDG. We also report the X-ray crystal structures of two KdgF proteins and propose a mechanism for catalysis. The discovery of the function of KdgF fills a 50-y-old gap in the knowledge of uronate metabolism. Our findings have implications not only for the understanding of an important metabolic pathway, but also the role of pectinolysis in plant-pathogen virulence and the growing interest in the use of pectin and alginate as feedstocks for biofuel production.uronate | ring opening | tautomerization | pectin | alginate P olysaccharides, such as those found as biomass in marine algae and terrestrial plants, comprise a vast sink of photosynthetically fixed carbon and a potentially enormous source of energy to organisms with the appropriate metabolic systems to unlock it. Pectin, a complex polyuronate largely made up of the uronate D-galacturonate connected by α-(1,4) linkages, is one such polysaccharide. The principal reservoir of pectin is the primary cell wall of terrestrial plants and, as such, its degradation and metabolism by microbes is an important component of the natural turnover of biomass, infection by plant pathogens, digestion of dietary fiber in the mammalian gut, and the utilization of biomass as feedstocks for biofuels or other valuable products (1). Similarly, alginate, another polyuronate that comprises β-linked D-mannuronate and L-guluronate (in varying lengths and arrangements), is a major cell wall component of brown macroalgae (seaweed). Alginate can comprise up to 40% of the dry weight of the algae, making the recycling of this photosynthetically fixed carbon a significant aspect of the ocean carbon cycle. The prevalence of both polysaccharides in biomass has made them important considerations in the production of ethanol from marine algae and terrestrial plant feedstocks (e.g., refs. 2-4).The microbial pathways responsible for the metab...

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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confidence: 99%

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KdgF, the missing link in the microbial metabolism of uronate sugars from pectin and alginate

Hobbs

Lee

Robb

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…The low sequence identity suggests that streptococcal genes coding for isomerase and dehydrogenase involved in the metabolism of glycosaminoglycans have been separately evolved from kduID, which is the operon for KduI and KduD, thus postulating that the streptococcal isomerase and dehydrogenase are designated as DhuI and DhuD, respectively, distinct from KduI and KduD. The operon kduID was first identified in Dickeya dadantii (36) and distributed in Escherichia, Klebsiella, Salmonella, Vibrio, and Yersinia (38). We also found kduID and kdgAK in the UGL genetic cluster in pathogenic Clostridium (39) and Enterococcus (40) (Fig.…”

Section: Classification Of the Ugl Genetic Clustermentioning

confidence: 99%

“…We have recently identified the enzyme (A1-R) gene in an alginate-assimilating bacterium (35). In pectin-assimilating bacteria, such as Dickeya and Pectobacterium, formerly known as Erwinia, ␣-keto acid, Dhu, from unsaturated galacturonic acid is converted to KDG via 3-deoxy-D-glycero-2,5-hexodiulosonate through subsequent reactions of KduI and 2-keto-3-deoxy-D-gluconate dehydrogenase (KduD) (36) (Fig. 1).…”

Section: Metabolism Of Unsaturated Uronic Acids From Glycosaminoglycansmentioning

confidence: 99%

Metabolic Fate of Unsaturated Glucuronic/Iduronic Acids from Glycosaminoglycans

Maruyama¹,

Oiki²,

Takase³

et al. 2015

Journal of Biological Chemistry

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Background: Some streptococci target host extracellular matrix glycosaminoglycans for infection. Results: The streptococcal metabolic pathway of glycosaminoglycan-derived unsaturated uronates was identified. The crystal structures of its isomerase and dehydrogenase were determined. Conclusion: Streptococci include an assembled genetic cluster for depolymerization, import, degradation, and metabolism of glycosaminoglycans. Significance: This study contributes to understanding of the streptococcal degradation/metabolism mechanism of glycosaminoglycans.

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The crystal structure of 5‐keto‐4‐deoxyuronate isomerase from Escherichia coli

Crowther

Georgiadis

2005

Proteins

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Analysis of an Erwinia chrysanthemi gene cluster involved in pectin degradation

Cited by 52 publications

References 0 publications

KdgF, the missing link in the microbial metabolism of uronate sugars from pectin and alginate

KdgF, the missing link in the microbial metabolism of uronate sugars from pectin and alginate

Metabolic Fate of Unsaturated Glucuronic/Iduronic Acids from Glycosaminoglycans

The crystal structure of 5‐keto‐4‐deoxyuronate isomerase from Escherichia coli

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