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Biosynthesis of vitamin B 2 in plants
Author(s) -
Fischer Markus,
Bacher Adelbert
Publication year - 2006
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.2006.00607.x
Subject(s) - biosynthesis , riboflavin , chemistry , biochemistry , ribulose , stereochemistry , phosphate , deamination , enzyme , pyruvate carboxylase
The biosynthesis of one riboflavin (vitamin B 2 ) molecule requires one molecule of GTP and two molecules of ribulose 5‐phosphate. The imidazole ring of GTP is hydrolytically opened, yielding a 2,5‐diaminopyrimidine that is converted to 5‐amino‐6‐ribitylamino‐2,4(1 H ,3 H )‐pyrimidinedione by a sequence of deamination, side chain reduction and dephosphorylation. Condensation of 5‐amino‐6‐ribitylamino‐2,4(1 H ,3 H )‐pyrimidinedione with 3,4‐dihydroxy‐2‐butanone 4‐phosphate obtained from ribulose 5‐phosphate yields 6,7‐dimethyl‐8‐ribityllumazine. Dismutation of the lumazine derivative yields riboflavin and 5‐amino‐6‐ribitylamino‐2,4(1 H ,3 H )‐pyrimidinedione, which is recycled in the biosynthetic pathway. Characteristic architectural features of most enzymes involved in the plant riboflavin pathway resemble those of eubacteria, whereas the similarities between plants and yeasts are less pronounced. Moreover, riboflavin biosynthesis in plants proceeds by the same reaction steps as in eubacteria, whereas fungi use a somewhat different pathway.