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Porcine small intestine evolved a specific offensive odor only 0.5 to 1 day after storage at 20 degrees C. We investigated the effects of Houttuyniae cordata (dokudami), refinery final molasses (RFM), green tea, and brown sugar on the evolution of methylmercaptan and ethanol, which were the main components of the volatiles which evolved from porcine small intestine in storage. Furthermore, we determined their antibacterial effect and deodorant activity against methylmercaptan, as possible factors in reducing the offensive odor. Addition of those materials reduced the offensive odor during storage. In particular, dokudami, green tea, and RFM markedly suppressed the evolution of methylmercaptan. RFM was most effective in suppressing the growth of bacteria. Dokudami had the highest deodorant activity, comparable to that of perilla leaves. However, the retardation of methylmercaptan evolution in situ cannot be simply explained by either of deodorant or antibacterial effect. It seems likely that the combined action of both effects affects the evolution of methylmercaptan in situ.

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Acid -soluble nucleotides from the mycelia were clearly separated by column chromatography on Dowex 1 X 2(HCOO-, 200 to 400 mesh). Under the experimental conditions used [2--14C] xanthine and [2--14C] guanine added were not incorporated into adenosine nucleotides but only into the guanosine nucleotides-GMP, GDP, GDP-Man, and GpA. Purines labeled at carbon 2 were effectively transferred to riboflavin but not radioactivity from [8--14C]--hypoxanthine was detected in the produced riboflavin. Comparison of the specific activity/time curves of guanosine nucleotides and riboflavin indicated that the specific activity of newly formed riboflavin coincides perfectly with that of GTP during incubation, and that the specific activity of accumulated riboflavin, at its maximum value, intersects the GTP curve. Thus, the kinetic studies with whole cells of E. ashbyii provide clear evidence that, among various nucleotides, GTP is the immediate precursor of riboflavin, and further attest that the intermediates involved in the biosynthetic pathway of the nucleotide precursor to riboflavin are in a trace amounts but have high turnover rates and, that the biosynthetic pathway has no salvage pathway for the intermediate derivatives, di- and tri-amino pyrimidines.

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In the present paper, the nucleotide precursor of riboflavin was investigated by experiments with labeled purines using non-growing cells of Eremothecium ashybii. The added purines, at 10(-4) M, were effectively incorporated into riboflavin at an early stage of riboflavin biosynthesis under the experimental conditions. In particular, both labeled xanthine and labeled guanine were specifically transported to guanosine nucleotides, GMP, GDP, GDP-Mannose and GTP, in the course of the riboflavin biosynthesis. A comparison of specific activities of labeled guanosine nucleotides and labeled riboflavin indicated that the nucleotide precursor of riboflavin is guanosine triphosphate. From the results obtained, a biosynthetic pathway of riboflavin is proposed under "DISCUSSION."

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When adenine was added to the non-growing cell medium of Eremothecium ashbyii, riboflavin production of the mold was increasingly inhibited with increasing concentration of adenine. Under these conditions, a cationic compound was accumulated in the mycelia. The compound was isolated from the mycelia and highly purified. The purified compound was proved to be S-adenosylhomocysteine through IR analysis. In the control experiment, or in the addition of other purines which stimulated riboflavin production of the mold, another cationic compound was accumulated in the non-growing cells. The compound was largely accumulated in the presence of both adenine and methionine, isolated from the mycelia and purified. The purified compound was concluded to be S-adenosylmethionine through IR and NMR analyses. The significance of these compounds on the riboflavin biosynthetic pathway was argued under "Discussion".

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This study was concerned with the detailed identification of the second product involved in the riboflavin synthetase reaction with riboflavin synthetase from Eremothecium ashbyii and a trapping agent, glyoxal.Thus, a green fluorescent compound accumulated during the incubation. The compound was purified through various column chromatography steps, and was examined by UV, IR, excitation and emission spectra and paper chromatography to prove that the isolated compound was 8-ribityllumazine. Accordingly it was concluded that a second product in riboflavin synthetase reaction was 4-ribitylamino-5-amino-2,6-dihydroxypyrimidine, the fragment, except for C-6 and C-7 of 8-ribityllumazine, being an incorporated glyoxal portion.

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