Biosynthesis of riboflavin: mechanism of formation of the ribitylamino linkage.
Feeding experiments with Ashbya gossypii followed by NMR analysis of the resulting riboflavin showed incorporation of deuterium from D-[2-2H]ribose at C-2' and from D-[1-2H]ribose in the pro-R position at C-1' of the ribityl side chain. The results rule out an Amadori rearrangement mechanism for the reduction of the ribosylamino to the ribitylamino linkage and point to formation of a Schiff base that is reduced stereospecifically opposite to the face from which the oxygen has departed. As prerequisite for the analysis, the 1H NMR signals for the pro-R and pro-S hydrogens at C-1' of 6,7-dimethyl-8-ribityllumazine and riboflavin and its tetraacetate were assigned with the aid of synthetic stereospecifically deuteriated samples.
D003903:Deuterium; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D012256:Riboflavin / Q000096:biosynthesis*; D012266:Ribose / Q000378:metabolism; D004718:Saccharomycetales / Q000378:metabolism*; D012545:Schiff Bases
D007202:Indicators and Reagents; D012545:Schiff Bases; D012266:Ribose; D003903:Deuterium; D012256:Riboflavin