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Spectrophotometric determination of ribose 1-phosphate
No full textIn the course of studies on nucleoside monophosphate metabolism, the need was encountered for a method to determine ribose-1-phosphate. Published assays for ribose-1-phosphate depend either on chromatographic separation of the sugarphosphate, or else on its acid lability which allows it to be determined as a phosphate. The present work describes a less laborious spectrophotometric assay which is both rapid and specific. The basis of the method is the absorbance change at 265 nm associated with the following two-stage enzymatic conversion: ribose-1-phosphate + adenine phosphate + adenosine (adenosine phosphorylase); adenosine + H2O → inosine + NH3 (adenosine deaminase). The change in absorbance was proportional to ribose-1-phosphate concentration at least up to 25 μg/ml. In tests of the assay, it was possible to detect ribose-1-phosphate formation from inosine and phosphate catalyzed by purine nucleoside phosphorylase. Further, the degradation of ribose-1-phosphate by various commercial phosphatases and several tissues or microbial extracts was observed
Utilization of exogenous purine compounds in Bacillus cereus: translocation of the ribose moiety of inosine
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Induction and repression of enzymes involved in exogenous purine compound utilization in Bacillus cereus
No full text5′-Nucleotidase, adenosine phosphorylase, adenosine deaminase and purine nucleoside phosphorylase, four enzymes involved in the utilization of exogenous purine compounds in Bacillus cereus, were measured in extracts of this organism grown in different conditions. It was found that adenosine deaminase is inducible by addition of adenine derivatives to the growth medium, and purine nucleoside phosphorylase by metabolizable purine and pyrimidine ribonucleosides. Adenosine deaminase is repressed by inosine, while both enzymes are repressed by glucose. Evidence is presented at during growth of B. cereus in the presence of AMP, the concerted action of 5′-nucleotidase and adenosine phosphorylase, two constitutive enzymes, leads to formation of adenine, and thereby to induction of adenosine deaminase. The ionsine formed would then cause induction of the purine nucleoside phosphorylase and repression of the deaminase. Taken together with our previous findings showing that purine nucleoside phosphorylase of B cereus acts as a translocase of the ribose moiety of ionsine inside the cell (Mura, U., Sgarrella, F. and Ipata, P.L. (1978) J. Biol. Chem. 253, 7905–7909), our results provide a clear picture of the molecular events leading to the utilization of the sugar moiety of exogenous AMP, adenosine and inosine as an energy source
Induction of deoxyribose 5-phosphate aldolase of Bacillus cereus by deoxyribonucleosides
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