No abstract

Ehrlich ascites tumor cells incubated in vitro with adenine-14C catabolized up to 20% of the radioactive nucleotides which were formed, principally via dephosphorylation of inosinate and xanthylate, with small amounts of adenylate and guanylate broken down. Cells incubated with hypoxanthine-14C catabolized a much larger proportion of nucleotides, principally via dephosphorylation of inosinate and xanthylate; guanylate was also broken down. Catabolic products of guanine-14C in these cells were xanthine, which was formed directly from guanine, and guanosine which at least in part was formed via dephosphorylation of guanylate.

No abstract

Ehrlich ascites tumor cells containing radioactive ATP were incubated in vitro with a range of concentrations of 2-deoxyglucose in order to produce different rates of ATP catabolism. Concentrations of all radioactive products of ATP catabolism were measured, and apparent rates of adenylate deaminase and inosinate dehydrogenase and of adenylate and inosinate dephosphorylation were calculated. It was concluded that these processes were reggulated primarily by the rate of formation of substrate, and to a lesser extent in some cases, by substrate concentration. No evidence was obtained for regulation of these processes by the concentration of ATP. The deoxyglucose-induced catabolism of radioactive GTP was also studied. When ATP catabolism was induced by incubation with 2,4-dinitrophenol, time courses of accumulation of purine nucleoside monophosphates and rates of alternative pathways of their metabolism were quite different than when deoxyglucose was used.

In human erythrocytes incubated with both naturally occurring purine nucleosides and with a variety of purine nucleoside analogs, ATP catabolism was accelerated and lactate accumulation was increased. Tubercidin was a particularly potent inducer of ATP catabolism. In cells incubated with tubercidin, the major route of adenylate metabolism was deamination, whereas in cells incubated with deoxyglucose, the major pathway was dephosphorylation.