Stimulatory Effects of Purines on Flavinogenesis by Non-Growing Cell of Eremothecium ashbyii

The immediate nucleotide precursor, guanosine triphosphate, in the riboflavin biosynthetic pathway.

“…These results are compatible with our previous data (7,8). Furthermore, the authors found the possibility that guanosine triphosphate is an immediate precursor of riboflavin in the nucleotide form, using a guanine analogue 8-aza -guanine in non-growing cells of E. ashbyii (9,10).…”

“…Previously, the present authors tried to determine the purine precursor using non-growing cells of a high flavinogenic mold, Eremothecium ashbyii. The results demonstrated that the different efficiencies of purines for flavinogenesis would depend upon the discrepancies between salvage pathways of exogenous purines and interconversion pathways of purines or purine nucleotides in different microorganisms or some times even in a same microorganism (7). However, the strong possibility was found that of the purines xanthine is the most immediate precursor of riboflavin, and is transferred to riboflavin via guanosine monophosphate in the experiments with growing or non-growing cells of E. ashbyii (7,8).…”

“…However, it remained unclear which purine is the most immediate precursor of riboflavin on the bio synthetic pathway, in spite of many laborious studies (1,(4)(5)(6). The present authors supposed that the different efficiencies of purines for flavinogenesis re sulted from the different activities of purine uptake and interconversions of purines and nucleotides in various microorganisms and even in a same microorganism (7,8).…”

Guanosine nucleotide precursor for flavinogenesis of Eremothecium ashbyii.

“…The present authors (9, 10) also reported that guanine and xanthine, especially the latter noticeably stimulates riboflavin biosynthesis of Eremothecium ashbyii. Furthermore, in non-growing cells of E. ashbyii (11), the present authors obtained the results (12,13) showing that riboflavin biosynthesis may proceed through GMP resulting from highly flavinogenic xanthine and the possibility (14) that gu anosine triphosphate is an immediate precursor at the level of purine nucleotide.…”

“…1. The biosynthetic pathway from exogenous xanthine to riboflavin was clarified in the previous paper (12) referring to the reports of BERLIN (16) and MAGER (17).…”