Concerning the enzymatic role of water-soluble vitamins many investigations have been published, but few papers are available on the mechanism of the action influencing lipid-soluble vitamins.Our recent interest in the biochemistry of lipid -soluble vitamins is an outgrowth of a curiosity about the correlation between vit amin D and sulfate metabolism.It was early reported by the present authors on the bioassay of vitamin D with rats fed on sterol-free synthetic diets and it was confirmed that no influence of vitamin B12 on the degree of healing in vitamin ID-deficient rats was observed (1).Thereafter many papers have been published on metabolic function of vitamin D, e.g., relation to calcium and phosphorus metabolism, relation to citrate metab olism and other metabolic relationships.Sano (2) summarized his researches on the rickets in Japan, e.g., thiamine and pyruvate levels in rachitic children, ribo flavin levels in blood and organs of experimental rachitic rabbits, phosphorus metab olism in young normal and rachitic rats, serum citrate levels in rachitic children and healing effect of cortisone on rachitic children. Keane et al. (3) reported that vitamin D markedly increased the absorption and retention of Ca45 given orally to chicks but no effect of the intramuscularly injected Ca45 was observed.It was concluded that the effect of vitamin D on calcium metabolism was primarily due to the absorption from the intestinal tract. Gershoff and Hegsted (4) fed diets containing various Ca/P ratios to chiks and found that the ratios had no significant effect on the intestinal absorption of Ca45 if an adequate amount of vitamin D was present.Otherwise, the calcium absorption was inverse ly proportional to Ca/P ratios.Cramer and Steenbock (5) found that the rise in calcium intake in the presence of vitamin D changed the negative calcium balance induced in rats by a low-phosphorus diet to a positive one.The relationship between vitamin D and citrate metabolism at the enzymatic level were investigated by DeLuca et al . (6). Addition of the vitamin to rachito genic or nonrachitogenic diets reduced the oxidation of citrate by kidney homo genates or mitochondria, but no effect was found on the oxidation of other Krebs cycle intermediates . These findings were presumed by the authors to account for 121
In the foregoing paper (1) the present authors studied the relationship between vitamin D potency and sulfate metabolism and higher level of sulfate in left tibia of chicks receiving vitamin D3 was demonstrated using S35-sulfate.
Metabolic correlation between nucleotide biogenesis and vitamin B12 have been reported and discussed by many investigators since the discovery of vitamin B12 in 1948 (1-2).In 1954, Rege et al. (3) reported that the DNA content of Lacto bacillus leichmannii might be proportionally variable to the amount of vitamin B12 added. Thereafter, in the microbioassay of vitamin B12, it has become well known that thymidine may be responsible for the growth of L. leichmannii even in the absence of vitamin B12.The present authors have attempted to examine whether another deoxyribonu cleosides could be formed from the corresponding ribonucleosides by washed cell suspension of L, leichmannii.At first, addition tests of various nucleosides or deoxyribonucleosides were carried out in the L. leichmannii assay of vitamin B12, using inosine (HxR), adenosine (AdR), guanosine (GuR) and thymidine (TdR). Positive effect was seen by a single addition of thymidine, but it was more marked after the addition of both vitamin B12 and thymidine.Additive tests of both vitamin B12 and ribonu cleosides were found to accelerate the growth rate of the strain in 3-4 hours but the effects were less than after a single addition of vitamin B12. Scarcely any effects were observed after a single addition of the ribonucleosides.Formation of deoxyadenosine from adenosine was first studied with the washed cell suspension of L, leichmannii, and the best condition for it was tested. Further studies on the formation of deoxyinosine were repeated using inosine, hypoxan thine, hypoxanthine plus D-ribose, hypoxanthine plus deoxyribose, adenine, adenine plus D-ribose, adenine plus deoxyribose, and the corresponding deoxyribonucleosides were found to be formed from the compound used in the experiment, but a single addition of D-ribose or deoxyribose was almost ineffective.
The authors (1) have reported the formation of deoxyinosine from inosine by cell washed suspension of Lactobacillus leichmannii ATCC 7830. Similar studies were further made using inosine-8-C14 and the washed cell suspension of the strain. First, the isolation and identification of the compounds which appeared in the reaction mixture were tried by two-dimensional paper chromatography and bioauto graphy and also the recovery of the standard compounds added to the reaction mixture. Then, the isolation and determination of 2•L-deoxyinosine-8-C14 were tested similarly, and the metabolic fate of inosine-8-C14 was examined.
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