α,β-Methylene-adenosine 5′-Triphosphate

Abstract The ATP analog, α,β-methylene-adenosine 5'-triphosphate (Ap(CH2)pp), competitively inhibits the basal as well as the glucagon- and NaF-stimulated activity of adenylate cyclase in isolated liver membrane preparations. The dissociation constant (Ki) of the inhibitor, 0.5 mm, is independent of the concentration of glucagon or NaF and is somewhat lower than the apparent Km for ATP. The phosphonic acid analog of ATP also inhibits competitively (Ki, 1.2 mm) the epinephrine-stimulated adenylate cyclase activity of membranes prepared from homogenates of isolated fat cells. The enzyme activity stimulated by NaF in these membranes is also inhibited by Ap(CH2)pp. The ADP analog, α,β-methylene-adenosine 5'-diphosphate does not significantly inhibit the activity of adenylate cyclase of liver cell membranes.