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Free keywords:
Acetates/*metabolism
Acetyl Coenzyme A/metabolism
Archaeal Proteins/metabolism
Fumarates/metabolism
Gene Transfer, Horizontal
Genes, Archaeal
Glutamic Acid/metabolism
Glyoxylates/metabolism
Haloarcula marismortui/enzymology/genetics/*metabolism
Malates/metabolism
Maleates/metabolism
*Metabolic Networks and Pathways
N-Methylaspartate/*metabolism
Oxidation-Reduction
Proteome
Succinic Acid/metabolism
Abstract:
Access to novel ecological niches often requires adaptation of metabolic pathways to cope with new environments. For conversion to cellular building blocks, many substrates enter central carbon metabolism via acetyl-coenzyme A (acetyl-CoA). Until now, only two such pathways have been identified: the glyoxylate cycle and the ethylmalonyl-CoA pathway. Prokaryotes in the haloarchaea use a third pathway by which acetyl-CoA is oxidized to glyoxylate via the key intermediate methylaspartate. Glyoxylate condensation with another acetyl-CoA molecule yields malate, the final assimilation product. This cycle combines reactions that originally belonged to different metabolic processes in different groups of prokaryotes, which suggests lateral gene transfer and evolutionary tinkering of acetate assimilation. Moreover, it requires elevated intracellular glutamate concentrations, as well as coupling carbon assimilation with nitrogen metabolism.
