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The gluconate shunt is an alternative route for directing glucose into the pentose phosphate pathway in fission yeast.

ABSTRACT: Glycolysis and the pentose phosphate pathway both play a central role in the degradation of glucose in all domains of life. Another metabolic route that can facilitate glucose breakdown is the gluconate shunt. In this shunt glucose dehydrogenase and gluconate kinase catalyze the two-step conversion of glucose into the pentose phosphate pathway intermediate 6-phosphogluconate. Despite the presence of these enzymes in many organisms, their only established role is in the production of 6-phosphogluconate for the Entner-Doudoroff pathway. In this report we performed metabolic profiling on a strain of Schizosaccharomyces pombe lacking the zinc-responsive transcriptional repressor Loz1 with the goal of identifying metabolic pathways that were altered by cellular zinc status. This profiling revealed that loz1? cells accumulate higher levels of gluconate. We show that the altered gluconate levels in loz1? cells result from increased expression of gcd1 By analyzing the activity of recombinant Gcd1 in vitro and by measuring gluconate levels in strains lacking enzymes of the gluconate shunt we demonstrate that Gcd1 encodes a novel NADP⁺-dependent glucose dehydrogenase that acts in a pathway with the Idn1 gluconate kinase. We also find that cells lacking gcd1 and zwf1, which encode the first enzyme in the pentose phosphate pathway, have a more severe growth phenotype than cells lacking zwf1 We propose that in S. pombe Gcd1 and Idn1 act together to shunt glucose into the pentose phosphate pathway, creating an alternative route for directing glucose into the pentose phosphate pathway that bypasses hexokinase and the rate-limiting enzyme glucose-6-phosphate dehydrogenase.

SUBMITTER: Corkins ME

PROVIDER: S-EPMC5566534 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature

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The gluconate shunt is an alternative route for directing glucose into the pentose phosphate pathway in fission yeast.

Corkins Mark E ME Wilson Stevin S Cocuron Jean-Christophe JC Alonso Ana P AP Bird Amanda J AJ

The Journal of biological chemistry 20170630 33

Glycolysis and the pentose phosphate pathway both play a central role in the degradation of glucose in all domains of life. Another metabolic route that can facilitate glucose breakdown is the gluconate shunt. In this shunt glucose dehydrogenase and gluconate kinase catalyze the two-step conversion of glucose into the pentose phosphate pathway intermediate 6-phosphogluconate. Despite the presence of these enzymes in many organisms, their only established role is in the production of 6-phosphoglu ...[more]

PMID: 28667014

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Project description:Bacillus megaterium is a bacterium of great importance as a plant-beneficial bacterium in agricultural applications and in industrial bioproduction of proteins. Understanding intracellular processing of carbohydrates in this species is crucial to predicting natural carbon utilization as well as informing strategies in metabolic engineering. Here, we applied stable isotope-assisted metabolomics profiling and metabolic flux analysis to elucidate, at high resolution, the connections of the different catabolic routes for carbohydrate metabolism immediately following substrate uptake in B. megaterium QM B1551. We performed multiple 13C tracer experiments to obtain both kinetic and long-term 13C profiling of intracellular metabolites. In addition to the direct phosphorylation of glucose to glucose-6-phosphate (G6P) prior to oxidation to 6-phosphogluconate (6P-gluconate), the labeling data also captured glucose catabolism through the gluconate pathway involving glucose oxidation to gluconate followed by phosphorylation to 6P-gluconate. Our data further confirmed the absence of the Entner-Doudoroff pathway in B. megaterium and showed that subsequent catabolism of 6P-gluconate was instead through the oxidative pentose-phosphate (PP) pathway. Quantitative flux analysis of glucose-grown cells showed equal partition of consumed glucose from G6P to the Embden-Meyerhof-Parnas (EMP) pathway and from G6P to the PP pathway through 6P-gluconate. Growth on fructose alone or xylose alone was consistent with the ability of B. megaterium to use each substrate as a sole source of carbon. However, a detailed 13C mapping during simultaneous feeding of B. megaterium on glucose, fructose, and xylose indicated non-uniform intracellular investment of the different carbohydrate substrates. Flux of glucose-derived carbons dominated the gluconate pathway and the PP pathway, whereas carbon flux from both glucose and fructose populated the EMP pathway; there was no assimilatory flux of xylose-derived carbons. Collectively, our findings provide new quantitative insights on the contribution of the different catabolic routes involved in initiating carbohydrate catabolism in B. megaterium and related Bacillus species.

Dataset Information

The gluconate shunt is an alternative route for directing glucose into the pentose phosphate pathway in fission yeast.

Publications

The gluconate shunt is an alternative route for directing glucose into the pentose phosphate pathway in fission yeast.

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