The hydrolysis of cyclic guanosine monophosphate (cyclic GMP) and of guanosine triphosphate (GTP) by the broken rods of the frog retina after a flash of light have been studied in vitro with a constant perfusion method. The activation has an onset apparently instantaneous as observed with the existing possible time resolution of 3 s. The activation is followed by a partial inactivation that does not bring the activity back to the pre-flash levl. GTP or the nonhdrolysable guanyl-5′-ylimidodiphosphate (GMP-PNP) is required for the normal light-activation of the phosphodiesterase and in its absence both the speed of activation and the sensitivity are greatly reduced. The activation speed, the sensitivity (threshold at approx. 0.00004% bleaching), and the kinetic constants do not exclude a direct role in the process of excitation for the phosphodiesterase and suggest a subsidiary but as yet undefined role for the GTPase. © 1979.
Phosphodiesterase and GTPase in rod outer segments kinetics in vitro / Caretta, A.; Cavaggioni, A.; Sorbi, R. T.. - In: BIOCHIMICA ET BIOPHYSICA ACTA-GENERAL SUBJECTS. - ISSN 0304-4165. - 583:1(1979), pp. 1-13. [10.1016/0304-4165(79)90303-9]
Phosphodiesterase and GTPase in rod outer segments kinetics in vitro
Caretta A.
Investigation
;Cavaggioni A.Funding Acquisition
;Sorbi R. T.Writing – Review & Editing
1979-01-01
Abstract
The hydrolysis of cyclic guanosine monophosphate (cyclic GMP) and of guanosine triphosphate (GTP) by the broken rods of the frog retina after a flash of light have been studied in vitro with a constant perfusion method. The activation has an onset apparently instantaneous as observed with the existing possible time resolution of 3 s. The activation is followed by a partial inactivation that does not bring the activity back to the pre-flash levl. GTP or the nonhdrolysable guanyl-5′-ylimidodiphosphate (GMP-PNP) is required for the normal light-activation of the phosphodiesterase and in its absence both the speed of activation and the sensitivity are greatly reduced. The activation speed, the sensitivity (threshold at approx. 0.00004% bleaching), and the kinetic constants do not exclude a direct role in the process of excitation for the phosphodiesterase and suggest a subsidiary but as yet undefined role for the GTPase. © 1979.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.