Growth on D-Lyxose of a Mutant Strain of Escherichia coli K12 Using a Novel Isomerase and Enzymes Related to D-Xylose Metabolism

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Abstract
E. coli K12 cannot grow on D-lyxose, but a mutant was isolated which can utilize D-lyxose as sole C and energy source for growth. D-Lyxose is transported into the bacteria by the D-xylose permease. The mutant constitutively synthesizes a new isomerase which is not inducible in the parent strain under any of the conditions tested. This enzyme, whose native substrate appears to be D-mannose, fortuitously converts D-lyxose into D-xylulose. Its structural gene is located at .apprx. 85 min on the E. coli genetic map, away from other known isomerase genes. D-Xylulose is subsequently catabolized by the enzymes of the normal D-xylose metabolic pathway. D-Mannose isomerase was partially purified and some of its properties were examined.