PMID:10217500
| Citation |
Stern, RJ, Lee, TY, Lee, TJ, Yan, W, Scherman, MS, Vissa, VD, Kim, SK, Wanner, BL and McNeil, MR (1999) Conversion of dTDP-4-keto-6-deoxyglucose to free dTDP-4-keto-rhamnose by the rmIC gene products of Escherichia coli and Mycobacterium tuberculosis. Microbiology (Reading, Engl.) 145 ( Pt 3):663-71 |
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| Abstract |
dTDP-rhamnose is made from glucose-1-phosphate and dTTP by four enzymes encoded by rmIA-D. An Escherichia coli rmIC mutant was constructed and a crude enzyme extract prepared from it did not produce dTDP-4-keto-rhamnose, in contrast to a crude enzyme extract prepared from a wild-type E. coli strain where small amounts of this intermediate were found after incubation with dTDP-glucose in the absence of NADPH. These results showed that dTDP-4-keto-rhamnose, the product of RmIC, exists as a free intermediate. Further, the Mycobacterium tuberculosis rmIC gene was expressed and incubation of the resulting purified M. tuberculosis RmIC enzyme with dTDP-4-keto-6-deoxyglucose resulted in the conversion of approximately 7% of dTDP-4-keto-6-deoxyglucose to dTDP-4-keto-rhamnose. The enzyme also allowed for the incorporation of two deuterium atoms from deuterium oxide solvent into dTDP-4-keto-glucose. Thus the rmIC gene encodes dTDP-4-keto-6-deoxyglucose epimerase capable of epimerizing at both C-3' and C-5'; this enzyme produces free dTDP-4-keto-rhamnose but the equilibrium of the 4-keto sugar nucleotides lies strongly on the side of the gluco configuration. |
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| Keywords |
Carbohydrate Epimerases/metabolism; Cloning, Molecular; Deuterium Oxide/metabolism; Escherichia coli/enzymology; Gene Deletion; Glucose/analogs & derivatives; Glucose/metabolism; Mutation; Mycobacterium tuberculosis/enzymology; Mycobacterium tuberculosis/genetics; Nucleoside Diphosphate Sugars/biosynthesis; Rhamnose/analogs & derivatives; Rhamnose/metabolism; Thymine Nucleotides/biosynthesis; Thymine Nucleotides/metabolism |
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