Maturation dependent decline of adenylate cyclase in rabbit red blood cell membranes

Adenylate cyclase (EC 4.6.1.1) was studied in membrane preparations of reticulocyte-rich blood obtained from phenylhydrazine-treated rabbits and compared to that of untreated animals.Basal and fluoride-stimulated activities were decreased 2- and 4-fold, respectively, during the process of maturation.Catalytic parameters such as time course, protein, ATP, Mg²⁺ concentration curves and K_m have been determined and were found to be similar in the reticulocyte and the erythrocyte.Adenylate cyclase was sensitive to GTP, 5′-guanylyl imidodiphosphate, prostaglandin E₁ and prostaglandin E₂. Activation by prostaglandin E₁ was higher than that produced by prostaglandin E₂. Only additive effect was found when 5′-guanylyl imidodiphosphate or GTP was added to hormone-stimulated activity. The sensitivity of the enzyme to these effectors was decreased over the transition reticulocyte-erythrocyte.In either cell the enzyme was not activated by catecholamines (epinephrine, norepinephrine, isoproterenol).