Adenine nucleoside 3′-tetraphosphates are novel and potent inhibitors of adenylyl cyclases

2'-Deoxyadenosine 3'-tetraphosphate (2'-deoxy-3'-A(4)P) and 2',5'-dideoxyadenosine 3'-tetraphosphate (2',5'-dideoxy-3'-A(4)P) were synthesized, and their effects were tested on crude and purified forms of native adenylyl cyclases isolated from brain. Syntheses combined the method of alkoxide activation with the use of tribromoethyl phosphoromorpholino-chloridate as an initial phosphorylating agent. Inhibition of adenylyl cyclase was rapid in onset. With 2'-d-3'-A(4)P or 2',5'-dd-3'-A(4)P inhibition of a purified native enzyme conformed to a linear noncompetitive behavior with respect to substrate, metal-5'ATP. Order of potency was 2',5'-dideoxy- > 2'-deoxyadenosine and 3'-tetraphosphate > 3'-triphosphate. Both mechanism of inhibition and rank order of potency were consistent with inhibition via the 3'-nucleotide-(P)-site on adenylyl cyclase. Neither 2',5'-dd-3'-ATP nor 2',5'-dd-3'-A(4)P had any effect on the activities of other adenosine nucleotide binding proteins such as Ca2+/calmodulin-sensitive cyclic nucleotide phosphodiesterase, Na+/K+-ATPase, or cAMP-dependent protein kinase. With purified adenylyl cyclase from bovine brain 2',5'-dd-3'-A(4)P and 2'-d-3'-A(4)P gave, respectively, IC50 values of 9.3 and 15 nM and K-i values of 23 and 53 nM. These 3'-nucleotides are the most potent regulators described for adenylyl cyclases.