Thymidine diphosphate mannose and thymidine diphosphate rhamnose in Streptomyces grieus

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Abstract
The nucleotide mixture obtained by alcoholic extraction of S. griseus contained several thymidine derivatives. Thymidine diphosphate mannose and thymidine diphosphate rhamnose were isolated from this source and their structures were established. Products detected in their acid hydrolysates include thymidine, inorganic phosphate and mannose or rhamnose. The 2 hexoses were identified chromatographically, and by reduction to the corresponding hexitols followed by treatment with acid. Hydrolysis with rattlesnake venom gave thymidine. The mannose possesses the D-configuration, since the nucleotide, after oxidation with periodate then bromine water followed by acid hydrolysis, gave D-glyceric acid. The configuration of the glyceric acid was established by enzymic phosphorylation and determination of D-glyceric acid 3-phosphate. The above method for determining the configuration of sugar phosphate residues is generally applicable. The stability of the mannose nucleotide towards ammonia, and the instability of the rhamnose nucleotide under comparable conditions, indicate that the former is an a-mannose derivative and the latter is a B-rhamnose derivative. Conformational aspects of these nucleotide structures are discussed. A chemical synthesis of thymidine diphosphate mannose is described. The enzymic conversion of thymidine diphosphate glucose into thymidine diphosphate mannose was observed and a possible mechanism for the biosynthesis of rhamnose is given. Other likely biochemical functions for the thymidine derivatives are discussed. These include a suggested scheme for the biosynthesis of streptose.