Genes for D-arabinitol and ribitol catabolism from Klebsiella pneumoniae

Abstract

The enzymes for catabolism of the pentitols D-arabinitol (Dal) and ribitol (Rbt) and the corresponding genes from Klebsiella pneurnoniae (dal and rbt) and Escherichia coli (at/ and rtl) have been used intensively in experimental evolutionary studies. Four dal and four rbt genes from the chromosome of K. pneurnoniae 1033-5P14 were cloned and sequenced. These genes are clustered in two adjacent but divergently transcribed operons and separated by two convergently transcribed repressor genes, dalR and rbtR. Each operon encodes an NAD-dependent pentose dehydrogenase (dalD and rbtl)), an ATP-dependent pentulose kinase (dalK and rbtK) and a pentose-specif ic ion symporter (dalT and rbtl). Although the biochemical reactions which they catalyse are highly similar, the enzymes showed interesting deviations. Thus, DalR (313 aa) and RbtR (270 aa) belong to different repressor families, and DalD (455 aa) and RbtD (248 aa), which are active as a monomer or as tetramers, respectively, belong to different dehydrogenase families. Of the two kinases (19.3% identity), DalK (487 aa) belongs to the subfamily of short 0-xylulokinases and RbtK (D-ribulokinase; 535 aa) to the subfamily of long kinases. The repressor, dehydrogenase and kinase genes did not show extensive similarity beyond local motifs. This contrasts with the ion symporters (86.6 Yo identity) and their genes (8207% identity). Due to their unusually high similarity, parts of dalT and rbtT have previously been claimed erroneously to correspond to 'inverted repeats' and possible remnants of a 'metabolic transposon' comprising the dal and rbt genes. Other characteristic structures, e.g. a secondary attl site and chi-like sites, as well as the conservation of this gene group in E. coli C are also discussed.

Arabitol Metabolism of Corynebacterium glutamicum and Its Regulation by AtlR

“…Growth on arabitol has been described for several microorganisms, e.g., for Enterobacter aerogenes (15,16,76,77), K. pneumoniae (34,35), Rhizobium meliloti and Rhizobium trifolii (53,62), E. coli C strains (64), and Pseudomonas fluorescens (13). All these organisms possess D-AraDH activity, mediated by NAD ϩ -dependent dehydrogenases (either AraDH or ManDH), and oxidize arabitol to D-xylulose, which is then phosphorylated by a XylK protein.…”

“…The formed xylulose-5-phosphate is further metabolized by reactions of the pentose phosphate pathway. For most of the arabitol-utilizing bacteria, the genes encoding AraDH and XylK and, in some bacteria, a gene also (putatively) encoding sugar transport proteins are transcribed as an operon, which is induced (derepressed) in response to D-arabitol (13,14,16,34,64,76). For some of these bacteria, e.g., E. aerogenes and K. pneumoniae, the genes encoding the respective repressors have also been localized in the close vicinity of the arabitol genes, being transcribed as a monocistronic unit in the opposite direction (16,34).…”

The genes for erythritol catabolism are organized as an inducible operon in Brucella abortus The GenBank accession number for the sequence reported in this paper is U57100.

“…Since this is the first description of an operon for erythritol utilization, comparisons are not possible. However, the analysis of operons for polyol utilization (Heuel et al, 1998) highlights the lack of a gene for erythritol transport. Erythritol was shown to be a substrate for the E. coli glycerol facilitator GlpF (Heller et al, 1980).…”

Characterization of Genes Involved inD-Sorbitol Oxidation in ThermotolerantGluconobacter frateurii

“…27) Our results for the perA mutant strain (Fig. 8) are the first experimental examples indicating the involvement of the specific transporter in the uptake of sugar alcohols in Gluconobacter, although no homologs with high identity were found in the genome of G. oxydans ATCC621H.…”