Adenylylimidodiphosphate: effect of contaminants on adenylate cyclase activity

Commercially available adenylylimidodiphosphate, APP(NH)P, appears to be contaminated with a variety of compounds. The effects of unpurified APP(NH)P on adenylate cyclase activity closely resembled the effects of guanylylimidodiphosphate (GPP(NH)P); that is, APP(NH)P alone caused a time-dependent, quasi-irreversible activation, and the stimulation of adenylate cyclase by APP(NH)P in combination with epinephrine was synergistic, eliminating the need for GTP. The GPP(NH)P-like activity of APP(NH)P could be separated from APP(NH)P by purification of the analogue on DEAE cellulose columns or by paper chromatography. The purified APP(NH)P does not appear to interest at the GTP site.