The regulatory control of β receptor dependent adenylate cyclase

The characteristics of the β receptor in turkey erythrocyte adenylate cyclase were studied using both kinetics of enzyme activation and direct binding measurement of the β agonists and antagonists to the β receptor. The regulatory ligands Gpp/(NH)p and Ca²⁺ do not have any direct effect on the β receptor, but modulate the enzyme activity through the interaction with specific regulatory sites. It was found that the role of the catecholamine hormone is to facilitate the activation of the enzyme by the guanyl nucleotide. The regulatory guanyl nucleotide binds to its allosteric site in the absence of hormone, but the activation of the enzyme is slow in the absence of hormone.