Biosynthesis of Riboflavin. Enzymatic Deamination of 2,5-Diamino-6-hydroxy-4-ribitylaminopyrimidine-5′-phosphate

Abstract

<jats:p>Cell extracts of Saccharomyces cerevisiae and Candida guilliermondii catalyze the hydrolytic deamination in position 2 of 2,5-diamino-6-hydroxy-4-ribitylaminopvrimidine 5′-phosphate. The deaminase activity is absent in rib 2 mutants of S. cerevisiae. These findings confirm the biosynthetic pathway proposed earlier on the basis of metabolic and genetic studies [2].</jats:p>

Biosynthesis of riboflavin: characterization of the bifunctional deaminase-reductase of Escherichia coli and Bacillus subtilis

“…Early studies with the yeast Saccharomyces cerevisiae showed that the reduction of the side chain precedes the deamination of the ring, and 2,5-diamino-6-ribitylamino-4(3H)-pyrimidinone 5Ј-phosphate (compound 4) was proposed as an intermediate (18). This sequence of reactions was later confirmed by enzymatic in vitro studies with Ashbya gossypii and S. cerevisiae (10,11,17).…”

Biosynthesis of Riboflavin: Structure and Properties of 2,5-Diamino-6-ribosylamino-4(3H)-pyrimidinone 5′-phosphate Reductase of Methanocaldococcus jannaschii

“…10,11 This sequence of reactions was later confirmed by enzymatic in vitro studies with Ashbya gossypii and Saccharomyces cerevisiae. [12][13][14] On the other hand, the deamination step (Figure 1, d) was shown to precede the side-chain reduction (Figure 1, e) in eubacteria 15 and in higher plants. 16 Early studies showed the basic pathway of riboflavin biosynthesis in Archaea to be similar to that of Eubacteria and fungi by in vivo studies with 13 C-labeled precursors.…”

“…[12][13][14] On the other hand, the deamination step (Figure 1, d) was shown to precede the side-chain reduction (Figure 1, e) in eubacteria 15 and in higher plants. 16 Early studies showed the basic pathway of riboflavin biosynthesis in Archaea to be similar to that of Eubacteria and fungi by in vivo studies with 13 C-labeled precursors. 17 5-Amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione 5′-phosphate (6) needs to be dephosphorylated prior to the enzymatic formation of 6,7-dimethyl-8-ribityllumazine (8), but the hypothetical phosphatase has not yet been described.…”

Biosynthetic precursors of deazaflavins

“…2) (15). Hydrolytic cleavage of the 2-amino group and reduction of the ribose side chain yield 5 -amino-6-ribitylamino-2,4(1H,3H) -pyrimidinedione 5-phosphate (compound 5) (2,18,22). Removal of the phosphate group yields 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione (compound 6), which is condensed with 3,4-dihydroxy-2-butanone 4-phosphate (compound 7) under formation of 6,7-dimethyl-8-ribityllumazine (compound 8).…”