DTDP-deoxyhexoses

Addition of dTDP-Glc-4,6-dehydratase (RmlB) to this module opens the door toward the diverse dTDP-deoxysugars. This enzyme catalyzes the formation of NDP-4-keto-6-deoxysugars, the common intermediate in almost all deoxyhexose biosynthetic pathways [50-52] (Fig. 4). 

Further progress has been made in the more complex conversions, involving the change in configuration at several carbon atoms, that occur in the process of formation of 6-deoxyhexoses, namely, the conversion of GDP-D-mannose into GDP-L-fucose, and dTDP-D-glucose into dTDP-L-rhamnose. 

Ftgun 38 General paih Yay for the biosynthesis of D- and L forn s of 6 deoxyhexose 6DOH). Hexose-l-P precursors are either D-glucosc-l-P or D-mannose l P- P phosphate NDP = dTDP, CDP.orGDP. 

Many of the naturally occurring secondary metabolites from bacteria and plants are glycosylated, mostly by 6-deoxyhexoses derived from dTDP-glucose (deoxythymidine 5 -diphospho glucose). 6-Deoxyhexose derivatives are present in a variety of antibiotics from actinomycetes, including macrolides, polyenes, and aminoglycosides, among others. 

Figure 10.7. Biosynthesis of 6-deoxyhexoses dTDP-L-rhamnose, GDP-D-rhamnose, and GDP-L-fucose.

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