Inhibition of adenylate cyclase by the 2',3'-dialdehyde of adenosine triphosphate

• Published in: The Journal of biological chemistry 1980-09, Vol.255 (18), p.8767-8771
• Main Authors: Westcott, K R, Olwin, B B, Storm, D R
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - analogs & derivatives; Adenosine Triphosphate - pharmacology; Adenylyl Cyclase Inhibitors; Animals; Cattle; Cell Membrane - enzymology; Cerebral Cortex - enzymology; Edetic Acid - pharmacology; Kinetics; Liver - enzymology; Magnesium - pharmacology; Manganese - pharmacology; Protein Binding; Rats
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)43567-3

The periodate-oxidized analog of ATP, 2',3'-dialATP, competitively inhibited bovine brain and rat liver adenylate cyclase. The apparent Ki for inhibition of brain adenylate cyclase by 2',3'-dialATP was 196 microM in the presence of Mg2+ and 37 microM in the presence of Mn2+. The Ki values for inhibition of rat liver adenylate cyclase by 2',3'-dialATP were 48 and 30 microM in the presence of Mg2+; and Mn2+, respectively. Adenylate cyclase activity was irreversibly inactivated by 2'3'-dialATP in the presence of NaCNBH3 and the kinetics for loss in enzyme activity were pseudo-first order. Both ATP and Tris protected adenylate cyclase from irreversible inhibition by 2',3'-dialATP and NaCNBH3. It is proposed that 2',3'-dialATP forms a Schiff's base with an amino group at the active site of the enzyme and that Na-CNBH3 reduction of this Schiff's base causes irreversible modification of the catalytic subunit. The Km for 2',3'-dialATP inactivation, the maximal rate constant of inactivation, and protection of the enzyme by ATP were not affected by the presence or absence of free Mg2+. These data indicate that a divalent cation is not required for binding of 2',3'-dialATP to the active site of adenylate cyclase.