Biosynthesis of vitamin b2 (riboflavin).
The biosynthesis of one riboflavin molecule requires one molecule of GTP and two molecules of ribulose 5-phosphate as substrates. The imidazole ring of GTP is hydrolytically opened, yielding a 4, 5-diaminopyrimidine which is converted to 5-amino-6-ribitylamino-2, 4(1H,3H)-pyrimidinedione by a sequence of deamination, side chain reduction and dephosphorylation. Condensation of 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione with 3, 4-dihydroxy-2-butanone 4-phosphate obtained from ribulose 5-phosphate affords 6,7-dimethyl-8-ribityllumazine. Dismutation of the lumazine derivative yields riboflavin and 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione, which is recycled in the biosynthetic pathway. The structure of the biosynthetic enzyme, 6,7-dimethyl-8-ribityllumazine synthase, has been studied in considerable detail.
Lehrstuhl für Organische Chemie und Biochemie, Lichtenbergstr. 4, D-85747 Garching, Federal Republic of Germany. adelbert.bacher@ch.tum.de
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Bacher
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Eberhardt
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Fischer
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Kis
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Richter
D001412:Bacillus subtilis / Q000201:enzymology; D004798:Enzymes / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D004926:Escherichia coli / Q000201:enzymology; D006136:GTP Cyclohydrolase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D006801:Humans; D012256:Riboflavin / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012258:Riboflavin Synthase / Q000378:metabolism*
D004798:Enzymes; D012258:Riboflavin Synthase; D006136:GTP Cyclohydrolase; D012256:Riboflavin