Formation of Deoxyinosine From Inosine by Washid Cell Suspension of Vitamin B12-Requiring Strain of Lactobacillus Leichmannii

Abstract

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.