Biogenesis of Riboflavin in Green Leaves

Studies on Plant Flavokinase

“…The biogenesis of riboflavin in green leaves and the enzymatic formation of the vitamin from 6, 7-dimethyl- 8-ribityllumazine were already demonstrated by the present authors (2)(3)(4)(5).…”

Identification of the second product of the riboflavin synthetase reaction.

“…The present authors have shown that only two molecules of 6, 7-dimethyl -8-ribityllumazine are obligatory as substrate for riboflavin synthetase reaction and no other compounds, such as 4-carbon derivatives, are needed with ribo fl avin synthetase from spinach leaves (1). Thereafter, the reaction mechanism, in which one of the substrates is a 4-carbon donor and another is an accepter in the formation of riboflavin skeleton, was verified by works with labelled 6, 7 dimethyl-8-ribityllumazine using enzymes from A. gossypii (5) and yeast (6).…”

“…9), which catalyzes the conversion of 6, 7 -dimethyl-8-ribityllumazine to riboflavin, has been detected in many organisms (1)(2)(3)(4). Furthermore, it has been clarified that the substrates in the reaction are only two molecules of 6, 7-dimethyl-8-ribityllumazine, one of which is the donor and another the accepter of 4-carbon, which is the building block of the o-xylene ring of the riboflavin molecule (1,5,6). Accordingly, it is easily supposed that the fragment, except for 4-carbon portion of 6, 7-dimethyl-8-ribityllumazine, 4-ribitylamino-5-amino-2, 6-dihydroxypyrimidine, can be one of the reaction products.…”

Biogenesis of Riboflavin in Green Leaves

“…These observations seem to exclude the possibilities of the re placement of diacetyl moiety of pyrazine ring of G compound by pyruvate, followed by the condensation of 4-ribitylamino-5-aminouracil and pyruvate. The evidence, in the experiments using enzyme preparations from various microorganisms and plants, that V compound derived directly from G compound, has been accumulated (5)(6)(7)(8).…”