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

Purine metabolism in relation to the riboflavin biosynthesis was examined using non-growing cell of Eremothecium ashbyii.1. It was found that xanthine is the most effective purine for flavinogenesis among various purines tested in the stimulation experiments using non-growing cell.2. The UV light absorption spectra of purines in non-growing cell medium were determined during the incubation. The conversions of adenine to hypoxanthine at the earlier stages and hypoxanthine to xanthine at the later stages were detected. Furthermore, the conversion of adenine to hypoxanthine was found to be located endogenously.3. The membrane transportable effects of purines were examined by photometrically determining the residual purines in the medium during the incubation and thus noticeable results which commonly have a unique plateau regions were obtained. However, any marked differences between added purines were not observed.4. Fluctuation of purine pools in cell was followed, using cation exchange resin, Dowex-50×4 in the presence of various purines. Thus, guanine was found to be accumulative but adenine was not detected in cell. Moreover, xanthine did not convert to any other purines and guanine also was not convertible except for its conversion to xanthine.5. Dynamic changes of purines in the 24 hr incubation medium were followed by the use of cation exchanger. However, the accumulation of particular purine derivatives was not observed.6. Only the third nucleotide fraction in the water eluting fraction of the column chromatography by cation exchanger characteristically fluctuated with the incubation. This fraction was found to consist of adenosine monophosphate and guanosine monophosphate. The changes of these nucleotides seem to be closely related to flavinogenesis.7. Xanthine contents inside and outside the cells at 24 hr of incubation were determined by using Florisil column and Dowex-50 column. Thus, guanine appeared to be converted to xanthine at the later stages of the incubation. Other purines were also well in accordance with the results of Summary 2.