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The nutritional status of Methanosarcina acetivorans regulates glycogen metabolism and gluconeogenesis and glycolysis fluxes
Author(s) -
SantiagoMartínez Michel Geovanni,
Encalada Rusely,
LiraSilva Elizabeth,
Pineda Erika,
GallardoPérez Juan Carlos,
ReyesGarcía Marco Antonio,
Saavedra Emma,
MorenoSánchez Rafael,
MarínHernández Alvaro,
JassoChávez Ricardo
Publication year - 2016
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.13717
Subject(s) - gluconeogenesis , glycogen , biochemistry , glycogen synthase , glycolysis , glycogen branching enzyme , glycogen debranching enzyme , glycogen phosphorylase , biology , citric acid cycle , phosphorylase kinase , metabolism , chemistry
Gluconeogenesis is an essential pathway in methanogens because they are unable to use exogenous hexoses as carbon source for cell growth. With the aim of understanding the regulatory mechanisms of central carbon metabolism in Methanosarcina acetivorans , the present study investigated gene expression, the activities and metabolic regulation of key enzymes, metabolite contents and fluxes of gluconeogenesis, as well as glycolysis and glycogen synthesis/degradation pathways. Cells were grown with methanol as a carbon source. Key enzymes were kinetically characterized at physiological pH/temperature. Active consumption of methanol during exponential cell growth correlated with significant methanogenesis, gluconeogenic flux and steady glycogen synthesis. After methanol exhaustion, cells reached the stationary growth phase, which correlated with the rise in glycogen consumption and glycolytic flux, decreased methanogenesis, negligible acetate production and an absence of gluconeogenesis. Elevated activities of carbon monoxide dehydrogenase/acetyl‐CoA synthetase complex and pyruvate: ferredoxin oxidoreductase suggested the generation of acetyl‐CoA and pyruvate for glycogen synthesis. In the early stationary growth phase, the transcript contents and activities of pyruvate phosphate dikinase, fructose 1,6‐bisphosphatase and glycogen synthase decreased, whereas those of glycogen phosphorylase, ADP ‐phosphofructokinase and pyruvate kinase increased. Therefore, glycogen and gluconeogenic metabolites were synthesized when an external carbon source was provided. Once such a carbon source became depleted, glycolysis and methanogenesis fed by glycogen degradation provided the ATP supply. Weak inhibition of key enzymes by metabolites suggested that the pathways evaluated were mainly transcriptionally regulated. Because glycogen metabolism and glycolysis/gluconeogenesis are not present in all methanogens, the overall data suggest that glycogen storage might represent an environmental advantage for methanosarcinales when carbon sources are scarce. Also, the understanding of the central carbohydrate metabolism in methanosarcinales may help to optimize methane production.