7/5/2023 0 Comments Glucose structure download![]() 2010), or the subunit of the archaellum filament FlaB (Meyer et al. 2000), the major surface (S-) layer protein SlaA (Peyfoon et al. In the hyperthermophilic archaeon Sulfolobus acidocaldarius sulfoquinovose is either a component of the glycosylated, membrane-associated cytochrome b complex (Zähringer et al. 2014), with cyanobacterial strains of the genus Spirulina having recently gained interest because of the anti-HIV properties of some of their sulfoquinovose-containing sulfolipids (Kwei et al. Among those is, for instance, the sulfolipid sulfoquinovosyl diacylglycerol which is found in the chloroplast membrane of plants and in cyanobacteria (Benning et al. UDP-sulfoquinovose is the nucleotide-activated form of sulfoquinovose (6-deoxy-6- C-sulfo- d-glucopyranose, Qui6S) and is required for the incorporation of sulfoquinovose into glycoconjugates. The obtained functional data are compared with those from other UDP-sulfoquinovose synthases. Deuterium labeling confirmed that dehydration of UDP- d-glucose occurs only from the enol form of UDP-4-keto-glucose. For the first time, the rapid initial electron transfer between UDP- d-glucose and NAD + could be monitored in a UDP-sulfoquinovose synthase. During the redox reaction the cofactor remains tightly bound to Agl3 and participates in the reaction in a concentration-dependent manner. In the absence of a sulfur donor, UDP- d-glucose is converted via UDP-4-keto- d-glucose to UDP- d-glucose-5,6- ene, the structure of which was determined by 1H and 13C-NMR spectroscopy. We propose that in vitro biosynthesis of UDP-sulfoquinovose occurs through an NAD +-dependent oxidation/dehydration/enolization/sulfite addition process. The obtained data suggest for Agl3 a modified dehydratase reaction mechanism. By comparison of sequence and structure of Agl3 and SQD1, putative catalytic amino acids of Agl3 were selected for mutational analysis. Based on the amino acid sequence, Agl3 belongs to the short-chain dehydrogenase/reductase enzyme superfamily, together with SQD1 from Arabidopsis thaliana, the only UDP-sulfoquinovose synthase with known crystal structure. The UDP-sulfoquinovose synthase Agl3 from Sulfolobus acidocaldarius converts UDP- d-glucose and sulfite to UDP-sulfoquinovose, the activated form of sulfoquinovose required for its incorporation into glycoconjugates.
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