Open AccessGuanosine diphosphate‐4‐keto‐6‐deoxy‐ d ‐mannose reductase in the pathway for the synthesis of GDP‐6‐deoxy‐ d ‐talose in Actinobacillus actinomycetemcomitans
Author(s) -
Suzuki Nao,
Nakano Yoshio,
Yoshida Yasuo,
Nezu Takashi,
Terada Yoshihiro,
Yamashita Yoshihisa,
Koga Toshihiko
Publication year - 2002
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1033.2002.03331.x
Subject(s) - mannose , chemistry , guanosine diphosphate , biochemistry , sodium cyanoborohydride , levansucrase , escherichia coli , nucleotide , biology , guanine , gene , bacteria , organic chemistry , genetics , bacillus subtilis
The serotype a‐specific polysaccharide antigen of Actinobacillus actinomycetemcomitans is an unusual sugar, 6‐deoxy‐ d ‐talose. Guanosine diphosphate (GDP)‐6‐deoxy‐ d ‐talose is the activated sugar nucleotide form of 6‐deoxy‐ d ‐talose, which has been identified as a constituent of only a few microbial polysaccharides. In this paper, we identify two genes encoding GDP‐6‐deoxy‐ d ‐talose synthetic enzymes, GDP‐α‐ d ‐mannose 4,6‐dehydratase and GDP‐4‐keto‐6‐deoxy‐ d ‐mannose reductase, in the gene cluster required for the biosynthesis of serotype a‐specific polysaccharide antigen from A. actinomycetemcomitans SUNYaB 75. Both gene products were produced and purified from Escherichia coli transformed with plasmids containing these genes. Their enzymatic reactants were analysed by reversed‐phase HPLC (RP‐HPLC). The sugar nucleotide produced from GDP‐α‐ d ‐mannose by these enzymes was purified by RP‐HPLC and identified by electrospray ionization‐MS, 1 H nuclear magnetic resonance, and GC/MS. The results indicated that GDP‐6‐deoxy‐ d ‐talose is produced from GDP‐α‐ d ‐mannose. This paper is the first report on the GDP‐6‐deoxy‐ d ‐talose biosynthetic pathway and the role of GDP‐4‐keto‐6‐deoxy‐ d ‐mannose reductase in the synthesis of GDP‐6‐deoxy‐ d ‐talose.