title: Arabinose is metabolized via a phosphoketolase pathway in Clostridium acetobutylicum ATCC 824.
abstract: In this report, a novel zymogram assay and coupled phosphoketolase assay were employed to demonstrate that Clostridium acetobutylicum gene CAC1343 encodes a bi-functional xylulose-5-P/fructose-6-P phosphoketolase (XFP). The specific activity of purified recombinant XFP was 6.9 U/mg on xylulose-5-P and 21 U/mg on fructose-6-P, while the specific activity of XFP in concentrated C. acetobutylicum whole-cell extract was 0.094 and 0.52 U/mg, respectively. Analysis of crude cell extracts indicated that XFP activity was present in cells grown on arabinose but not glucose and quantitative PCR was used to show that CAC1343 mRNA expression was induced 185-fold during growth on arabinose when compared to growth on glucose. HPLC analysis of metabolites revealed that during growth on xylose and glucose more butyrate than acetate was formed with final acetate:butyrate ratios of 0.72 and 0.83, respectively. Growth on arabinose caused a metabolic shift to more oxidized products with a final acetate:butyrate ratio of 1.95. The shift towards more oxidized products is consistent with the presence of an XFP, suggesting that arabinose is metabolized via a phosphoketolase pathway while xylose is probably metabolized via the pentose phosphate pathway.
authors.affiliation: Sensors and Electron Devices Directorate, US Army Research Laboratory, 2800 Powder Mill Road, Adelphi, MD 20783, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Servinsky
authors.forename: K L
authors.initials: KL
authors.lastname: Germane
authors.forename: S
authors.initials: S
authors.lastname: Liu
authors.forename: J T
authors.initials: JT
authors.lastname: Kiel
authors.forename: A M
authors.initials: AM
authors.lastname: Clark
authors.forename: J
authors.initials: J
authors.lastname: Shankar
authors.forename: C J
authors.initials: CJ
authors.lastname: Sund
mesh_terms: D000446:Aldehyde-Lyases / Q000378:metabolism*; D001089:Arabinose / Q000378:metabolism*; D046969:Clostridium acetobutylicum / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D005632:Fructose / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D005947:Glucose / Q000378:metabolism; D010427:Pentose Phosphate Pathway; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014994:Xylose / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D005632:Fructose; D014994:Xylose; D001089:Arabinose; D000446:Aldehyde-Lyases; C022367:phosphoketolase; D005947:Glucose