During metabolic evolution to improve @entity4588 production in @entity526 strains, significant changes in cellular metabolism were acquired that increased energy efficiency in two respects. The energy-conserving @entity7954 ( @entity7955 ) carboxykinase (pck), which normally functions in the reverse direction (gluconeogenesis; @entity413 repressed) during the oxidative metabolism of organic acids, evolved to become the major carboxylation pathway for @entity4588 production. Both PCK enzyme activity and gene expression levels increased significantly in two stages because of several mutations during the metabolic evolution process. High-level expression of this enzyme-dominated @entity515 fixation and increased @entity855 yield (1 @entity855 per @entity5911 ). In addition, the native PEP-dependent phosphotransferase system for @entity413 uptake was inactivated by a mutation in ptsI. This @entity413 transport function was replaced by increased expression of the GalP permease (galP) and glucokinase (glk). Results of deleting individual transport genes confirmed that GalP served as the dominant @entity413 transporter in evolved strains. Using this alternative transport system would increase the pool of PEP available for redox balance. This change would also increase energy efficiency by eliminating the need to produce additional PEP from @entity2388 , a reaction that requires two @entity855 equivalents. Together, these changes converted the wild-type @entity526 fermentation pathway for @entity4588 into a functional equivalent of the native pathway that nature evolved in @entity4588 -producing rumen bacteria.

Metabolic evolution of energy-conserving pathways for @entity4588 production in XXXX .

@entity7955 :: ('MESH:C073248', 'Chemical') :: ['PEP'] @entity4588 :: ('MESH:D019802', 'Chemical') :: ['succinate'] @entity7954 :: ('MESH:D010728', 'Chemical') :: ['phosphoenolpyruvate'] @entity515 :: ('CHEBI:29334', 'Chemical') :: ['CO(2)'] @entity855 :: ('MESH:D000255', 'Chemical') :: ['ATP'] @entity5911 :: ('MESH:D062907', 'Chemical') :: ['oxaloacetate'] @entity2388 :: ('MESH:D019289', 'Chemical') :: ['pyruvate'] @entity413 :: ('MESH:D005947', 'Chemical') :: ['glucose'] @entity526 :: ('562', 'Species') :: ['Escherichia coli', 'E. coli']
@entity526 :: (562,Species) :: ['Escherichia coli']
