Light regulation of cGMP metabolism in toad rod outer segments (ROS) deduced from intact photoreceptor and cellfree kinetics
Abstract
The rate of cGMP hydrolysis by phosphodiesterase (PDE) in intact ROS, monitored in dark-adapted isolated toad retina by the rate of /sup 18/O appearance in guanine nucleotide ..cap alpha..-phosphoryls, is 1/360th of that observed in disrupted ROS at a substrate concentration equivalent to the total (cGMP) in ROS. Low to moderate photic stimuli increase this cGMP hydrolytic rate up to 10-fold in intact ROS with little or no change in total (cGMP). G-protein activation determined in intact ROS by the fraction of GDP labeled with /sup 18/O corresponds with light-related increases in cGMP flux. In contrast, relatively high intensities and extended illumination cause attenuation of maximal cGMP hydrolysis with proportionate reductions in total (cGMP). From these observations combined with the effects of activated G-protein on kinetics and cGMP binding of ROS PDE the following model for light-regulation of cGMP metabolism was deduced: cGMP flux in intact ROS is severely restricted in the dark state because approximately 99% of the cGMP is bound to high affinity sites on the non-stimulated form of PDE. This constraint is relieved when activated G-protein converts the cGMP-binding form of PDE to a high K/sub m/ catalytic form. cGMP is then redistributed to a dynamic poolmore »
- Authors:
- Publication Date:
- Research Org.:
- Univ. of Minnesota, Minneapolis
- OSTI Identifier:
- 6372218
- Report Number(s):
- CONF-870644-
Journal ID: CODEN: FEPRA; TRN: 87-034060
- Resource Type:
- Conference
- Journal Name:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)
- Additional Journal Information:
- Journal Volume: 46:6; Conference: 78. annual meeting of the American Society of Biological Chemists conference, Philadelphia, PA, USA, 7 Jun 1987
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 59 BASIC BIOLOGICAL SCIENCES; CYCLASES; ENZYME ACTIVITY; NUCLEOTIDES; BIOCHEMICAL REACTION KINETICS; METABOLISM; PHOSPHODIESTERASES; EYES; FROGS; OXYGEN 18; TRACER TECHNIQUES; VISIBLE RADIATION; AMPHIBIANS; ANIMALS; AQUATIC ORGANISMS; BODY; BODY AREAS; ELECTROMAGNETIC RADIATION; ENZYMES; ESTERASES; EVEN-EVEN NUCLEI; FACE; HEAD; HYDROLASES; ISOTOPE APPLICATIONS; ISOTOPES; KINETICS; LIGHT NUCLEI; LYASES; NUCLEI; ORGANIC COMPOUNDS; ORGANS; OXYGEN ISOTOPES; RADIATIONS; REACTION KINETICS; SENSE ORGANS; STABLE ISOTOPES; VERTEBRATES; 550501* - Metabolism- Tracer Techniques
Citation Formats
Dawis, S M, Graeff, R M, Heyman, R A, Walseth, T F, and Butz, E A. Light regulation of cGMP metabolism in toad rod outer segments (ROS) deduced from intact photoreceptor and cellfree kinetics. United States: N. p., 1987.
Web.
Dawis, S M, Graeff, R M, Heyman, R A, Walseth, T F, & Butz, E A. Light regulation of cGMP metabolism in toad rod outer segments (ROS) deduced from intact photoreceptor and cellfree kinetics. United States.
Dawis, S M, Graeff, R M, Heyman, R A, Walseth, T F, and Butz, E A. 1987.
"Light regulation of cGMP metabolism in toad rod outer segments (ROS) deduced from intact photoreceptor and cellfree kinetics". United States.
@article{osti_6372218,
title = {Light regulation of cGMP metabolism in toad rod outer segments (ROS) deduced from intact photoreceptor and cellfree kinetics},
author = {Dawis, S M and Graeff, R M and Heyman, R A and Walseth, T F and Butz, E A},
abstractNote = {The rate of cGMP hydrolysis by phosphodiesterase (PDE) in intact ROS, monitored in dark-adapted isolated toad retina by the rate of /sup 18/O appearance in guanine nucleotide ..cap alpha..-phosphoryls, is 1/360th of that observed in disrupted ROS at a substrate concentration equivalent to the total (cGMP) in ROS. Low to moderate photic stimuli increase this cGMP hydrolytic rate up to 10-fold in intact ROS with little or no change in total (cGMP). G-protein activation determined in intact ROS by the fraction of GDP labeled with /sup 18/O corresponds with light-related increases in cGMP flux. In contrast, relatively high intensities and extended illumination cause attenuation of maximal cGMP hydrolysis with proportionate reductions in total (cGMP). From these observations combined with the effects of activated G-protein on kinetics and cGMP binding of ROS PDE the following model for light-regulation of cGMP metabolism was deduced: cGMP flux in intact ROS is severely restricted in the dark state because approximately 99% of the cGMP is bound to high affinity sites on the non-stimulated form of PDE. This constraint is relieved when activated G-protein converts the cGMP-binding form of PDE to a high K/sub m/ catalytic form. cGMP is then redistributed to a dynamic pool where it is available to PDE catalytic sites and lower affinity allosteric sites. The (cGMP) in the dynamic pool is maintained or further increased or decreased by modulating the activity of an apparently light-sensitive guanylyl cyclase.},
doi = {},
url = {https://www.osti.gov/biblio/6372218},
journal = {Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)},
number = ,
volume = 46:6,
place = {United States},
year = {Fri May 01 00:00:00 EDT 1987},
month = {Fri May 01 00:00:00 EDT 1987}
}