title: Phosphoketolase pathway for xylose catabolism in Clostridium acetobutylicum revealed by 13C metabolic flux analysis.
abstract: Solvent-producing clostridia are capable of utilizing pentose sugars, including xylose and arabinose; however, little is known about how pentose sugars are catabolized through the metabolic pathways in clostridia. In this study, we identified the xylose catabolic pathways and quantified their fluxes in Clostridium acetobutylicum based on [1-(13)C]xylose labeling experiments. The phosphoketolase pathway was found to be active, which contributed up to 40% of the xylose catabolic flux in C. acetobutylicum. The split ratio of the phosphoketolase pathway to the pentose phosphate pathway was markedly increased when the xylose concentration in the culture medium was increased from 10 to 20 g liter(-1). To our knowledge, this is the first time that the in vivo activity of the phosphoketolase pathway in clostridia has been revealed. A phosphoketolase from C. acetobutylicum was purified and characterized, and its activity with xylulose-5-P was verified. The phosphoketolase was overexpressed in C. acetobutylicum, which resulted in slightly increased xylose consumption rates during the exponential growth phase and a high level of acetate accumulation.
authors.affiliation: Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.
authors.forename: Lixia
authors.initials: L
authors.lastname: Liu
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Tang
authors.forename: Yang
authors.initials: Y
authors.lastname: Gu
authors.forename: Qiang
authors.initials: Q
authors.lastname: Hua
authors.forename: Sheng
authors.initials: S
authors.lastname: Yang
authors.forename: Weihong
authors.initials: W
authors.lastname: Jiang
authors.forename: Chen
authors.initials: C
authors.lastname: Yang
mesh_terms: D000085:Acetates; D000446:Aldehyde-Lyases / Q000378:metabolism*; D002244:Carbon / Q000378:metabolism*; D002247:Carbon Isotopes; D046969:Clostridium acetobutylicum / Q000145:classification / Q000201:enzymology* / Q000378:metabolism; D005285:Fermentation; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D009154:Mutation; D010428:Pentosephosphates; D014994:Xylose / Q000378:metabolism*
chemical_list: D000085:Acetates; D002247:Carbon Isotopes; D010428:Pentosephosphates; C031625:xylulose-5-phosphate; D002244:Carbon; D014994:Xylose; D000446:Aldehyde-Lyases; C022367:phosphoketolase