DIFFERENCES IN THE METABOLISM AND METABOLIC EFFECTS OF THE CARBOCYCLIC ADENOSINE-ANALOGS, NEPLANOCIN A AND ARISTEROMYCIN

  • 1 April 1986
    • journal article
    • research article
    • Vol. 29  (4) , 383-390
Abstract
Neplanocin A and aristeromycin are carbocyclic adenosine analogs that differ only in the naplanocin A contains a double bond in the carbocyclic ring in aristeromycin is saturated. We have compared the metabolism and some of the metabolic effects of neplanocin A and synthetic (.+-.)-aristeromycin (C-Ado) in murine leukemia L1210 cells in culture. C-Ado, as shown earlier, was not only converted to its own phosphates but also was metabolized to carbocyclic guanosine. Both rapidly proliferating and slowly proliferating or resting cells phosphorylated C-Ado, but C-Ado was not converted to phosphates of carbocyclic guanosine in detectable amounts in cells whose growth had reached a plateau. When the metabolism of neplanocin and C-Ado was examined in the same experiment, both analogs were converted to the triphosphate analogs of ATP; no conversion of neplanocin A to the corresponding carbocylic analogs of guanine nucleotides was detected, whereas C-Ado was converted to the carbocyclic analog of GTP in amounts that approximated the GTP pool. This difference in metabolism was associated with a marked difference in effects of the two analogs on the utilization of hypoxanthine and guanine which was inhibited by C-Ado but not by neplanocin. The failure of neoplanocin A to be converted to analogs of guanine nucleotides apparently is the result of poor capacity of its monophosphate to serve as a substrate for AMP deaminase; the Vmax for deamination of neoplanocin-5'' monophosphate by this enzyme was only 5% of that for C-Ado monophosphate. In contrast, neplanocin A was a better substrate than C-Ado for adenosine deaminase.