The Distinctive Occurrence of Acid-Soluble Inosine in Rat Liver Microsomal Preparations

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Abstract
Rat liver microsomes were prepared by differential centrifugation (105,000 g, 60 min.) of a 0.25 [image] sucrose homogenate. Perchloric acid extracts were placed on dowex-1 ion exchange columns (formate form). The only compound absorbing in the UV which was eluted from the columns were found to be inosine, as evidenced by various chemical determinations and by paper chromatography. This compound is not found in rat liver mitochondria, which however has similar amounts (0.1 micromole per gram wet weight tissue) of the adenine nucleotides, AMP, ADP, ATP. The inosine was found to be weakly bound to the microsomal structure. Its principal route of formation in the microsomes is by the dephosphorylation of IMP, and it is not degraded there to hypoxanthine or to xanthine. Various enzymatic assays with microsomes gave negative results as to its possible function as a coenzyme.