Characterization of xylitol-utilizing mutants of Erwinia uredovora.
Of the four pentitols ribitol, xylitol, D-arabitol, and L-arabitol, Erwinia uredovora was able to utilize only D-arabitol as a carbon and energy source. Although attempts to isolate ribitol- or L-arabitol-utilizing mutants were unsuccessful, mutants able to grow on xylitol were isolated at a frequency of 9 X 10(-8). Xylitol-positive mutants constitutively synthesized both a novel NAD-dependent xylitol-4-dehydrogenase, which oxidized xylitol to L-xylulose, and an L-xylulokinase. The xylitol dehydrogenase had a Km for xylitol of 48 mM and showed best activity with xylitol and D-threitol as substrates. However, D-threitol was not a growth substrate for E. uredovora, and its presence did not induce either dehydrogenase or kinase activity. Attempts to determine the origin of the xylitol catabolic enzymes were unsuccessful; neither enzyme was induced on any growth substrate or in the presence of any polyol tested. Analysis of xylitol-negative mutants isolated after Tn5 mutagenesis suggested that the xylitol dehydrogenase and the L-xylulokinase structural genes were components of two separate operons but were under common regulatory control.
Doten
R C
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Mortlock
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D050542:D-Xylulose Reductase; D004885:Erwinia / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D009154:Mutation; D010770:Phosphotransferases / Q000032:analysis; D017853:Phosphotransferases (Alcohol Group Acceptor); D013401:Sugar Alcohol Dehydrogenases / Q000032:analysis; D014993:Xylitol / Q000378:metabolism*
D013401:Sugar Alcohol Dehydrogenases; D050542:D-Xylulose Reductase; D010770:Phosphotransferases; D017853:Phosphotransferases (Alcohol Group Acceptor); C032700:xylulokinase; D014993:Xylitol