Cloning and characterization of a novel gene encoding ?-ribose isomerase from Acinetobacter sp. strain DL-28 in Escherichia coli

Characterization of a Novel d -Lyxose Isomerase from Cohnella laevoribosii RI-39 sp. nov

“…The deduced amino acid sequence of CLLI exhibited no significant homology to any other sugar isomerase, including the RI from Acinetobacter sp. (30). However, a BLAST search with lyxA revealed that CLLI exhibited significant levels of sequence homology (Ն60%) with proteins from Bacillus species (Fig.…”

“…This enzyme is the first genetically identified isomerase that can catalyze the interconversion of D-lyxose to Dxylulose with a high specific activity. Although CLLI also converted D-mannose and L-ribose to D-fructose and L-ribulose, respectively, the amino acid sequence of the enzyme does not exhibit significant homology to MIs or RIs that can also isomerize D-lyxose (18,30). In addition, the substrate specificity of CLLI is different from the substrate specificities of MIs and RIs, suggesting that the enzyme is a novel LI.…”

“…Recently, an L-ribose isomerase (RI) catalyzing the reversible conversion of L-ribulose to L-ribose, as well as the conversion of D-lyxose to D-xylulose, was isolated from Acinetobacter sp. strain DL-28 (30,35). No enzyme of this type was previously known to exist.…”

“…No enzyme of this type was previously known to exist. This enzyme was induced by D-lyxose as a carbon source, and it was 47% and 4% as active on D-lyxose and D-mannose, respectively, as it was on L-ribose indicating that it may permit growth not only on Lribose but also on D-lyxose as a carbon source (30). However this observation needs to be confirmed since Escherichia coli mutants that are able to utilize L-ribose for growth do so not via an L-ribose and/or D-lyxose isomerase but via the ribitol pathway (42).…”

“…However, D-lyxose (the 2-epimer of D-xylose) is not found in many microorganisms, and the mechanisms of transport and metabolism of this compound are not well defined. During the past few decades several enzymes have been proposed to catalyze the isomerization of D-lyxose to D-xylulose (3,17,18,30). Some examples of these enzynes are the D-mannose isomerases (MI) (E.C.…”