title: Presence of a novel phosphopentomutase and a 2-deoxyribose 5-phosphate aldolase reveals a metabolic link between pentoses and central carbon metabolism in the hyperthermophilic archaeon Thermococcus kodakaraensis.
abstract: Numerous bacteria and mammalian cells harbor two enzymes, phosphopentomutase (PPM) and 2-deoxyribose 5-phosphate aldolase (DERA), involved in the interconversion between nucleosides and central carbon metabolism. In this study, we have examined the presence of this metabolic link in the hyperthermophilic archaeon, Thermococcus kodakaraensis KOD1. A search of the genome sequence of this strain revealed the presence of a closely related orthologue (TK2104) of bacterial DERA genes while no orthologue related to previously characterized PPM genes could be detected. Expression, purification, and characterization of the TK2104 protein product revealed that this gene actually encoded a DERA, catalyzing the reaction through a class I aldolase mechanism. As PPM activity was detected in T. kodakaraensis cells, we partially purified the protein to examine its N-terminal amino acid sequence. The sequence corresponded to a gene (TK1777) similar to phosphomannomutases within COG1109 but not COG1015, which includes all previously identified PPMs. Heterologous gene expression of TK1777 and characterization of the purified recombinant protein clearly revealed that the gene indeed encoded a PPM. Both enzyme activities could be observed in T. kodakaraensis cells under glycolytic and gluconeogenic growth conditions, whereas the addition of ribose, 2-deoxyribose, and 2'-deoxynucleosides in the medium did not lead to a significant induction of these activities. Our results clearly indicate the presence of a metabolic link between pentoses and central carbon metabolism in T. kodakaraensis, providing an alternative route for pentose biosynthesis through the functions of DERA and a structurally novel PPM.
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
authors.forename: Naeem
authors.initials: N
authors.lastname: Rashid
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Imanaka
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Fukui
authors.forename: Haruyuki
authors.initials: H
authors.lastname: Atomi
authors.forename: Tadayuki
authors.initials: T
authors.lastname: Imanaka
mesh_terms: D000446:Aldehyde-Lyases / Q000235:genetics / Q000502:physiology*; D002244:Carbon / Q000378:metabolism*; D004492:Edetic Acid / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D010429:Pentoses / Q000378:metabolism*; D010770:Phosphotransferases / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000302:isolation & purification; D012267:Ribosemonophosphates / Q000378:metabolism*; D013379:Substrate Specificity; D013696:Temperature; D019712:Thermococcus / Q000235:genetics / Q000378:metabolism*
chemical_list: D010429:Pentoses; D011994:Recombinant Proteins; D012267:Ribosemonophosphates; D002244:Carbon; C058245:2-deoxyribose 5-phosphate; D004492:Edetic Acid; D010770:Phosphotransferases; D000446:Aldehyde-Lyases; C020019:deoxyribose-phosphate aldolase; C022375:phosphopentomutase