Of the roles of ATP and GDP in the of photoinduced activation of 3',5'-cyclic GMP phosphodiesterase by rhodopsin from vertebrate retina photoreceptor membranes

Using a reconstructed system, composed of washed and illuminated bovine rod outer segment (ROS) membrane and nonpurified extract from ROS, ATP was shown to activate phosphodiesterase with the same efficiency as GTP at the concentrations down to 2 x 10(-6) M. In the presence of GDP (10(-6) M), the phosphodiesterase activity can be significantly enhanced by ATP (10(-6) M). The initial rate of the phosphodiesterase activity in the presence of GTP (10(-6) M) was higher than that in the presence of GppNHp at the same concentration.