title: Effects of adenosine and its derivatives on protein kinase activity of beef thyroid.
abstract: Effects of adenosine and some of its derivatives on beef protein kinase activity were investigated in vitro. Adenosine rapidly inhibited protein kinase activity in a dose-dependent manner. Significant inhibition occurred with 10 muM and half-maximal inhibition at 100 muM adenosine. Inhibition was almost complete with 5 mM adenosine. Inhibition was similar whether protein kinase activity was assayed with or without cyclic AMP. The inhibition  by adenosine was reversed by increasing the concentration of ATP and Lineweaver-Burk analysis indicated that adenosine inhibition was competitive with ATP. Addition of adenosine deaminase to the incubation medium prevented the inhibition induced by adenosine. Intact 1 and N6 positions of adenosine were important for the inhibition since their modification was associated with loss of inhibition. Modification of the 8 position of adenosine decreased, but did not abolish, the inhibition. The 2 and 3 position of ribose did not seem to be critical since 2- and 3-deoxyadenosine produced inhibition similar to that of adenosine.
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D002417:Cattle; D000242:Cyclic AMP / Q000494:pharmacology; D007700:Kinetics; D011494:Protein Kinases / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013961:Thyroid Gland / Q000187:drug effects / Q000201:enzymology*
chemical_list: D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D011494:Protein Kinases; D000241:Adenosine