Cyclic nucleotide phosphodiesterases in cultured normal and RCS rat pigment epithelium: Kinetics of cyclic AMP and cyclic GMP hydrolysis
| Autor: | Ross B. Edwards, Susan Y. Schmidt, Mary J. Kurtz |
|---|---|
| Rok vydání: | 1987 |
| Předmět: |
Phagocytosis
Kinetics chemistry.chemical_element Biology Calcium Cellular and Molecular Neuroscience Pigment 3' 5'-Cyclic-GMP Phosphodiesterases Cyclic AMP medicine Animals Magnesium Pigment Epithelium of Eye Cyclic GMP Magnesium ion Cells Cultured Phosphodiesterase Rats Inbred Strains Sensory Systems Epithelium Rats Enzyme Activation Ophthalmology medicine.anatomical_structure Biochemistry chemistry 3' 5'-Cyclic-AMP Phosphodiesterases visual_art visual_art.visual_art_medium Ultracentrifuge |
| Zdroj: | Experimental Eye Research. 45:67-75 |
| ISSN: | 0014-4835 |
| DOI: | 10.1016/s0014-4835(87)80079-9 |
| Popis: | Kinetically distinct classes of cyclic AMP (cAMP) and cyclic GMP (cGMP) phosphodiesterase activities (PDEs) were detected in homogenates of cultured pigment epithelium (PE) from both normal and Royal College of Surgeons (RCS) rats. PDE activities with apparent low Michaelis constants (Low K m cAMP-and cGMP-PDEs) were associated with the supernatant, while PDE activities with apparent high Michaelis constants (high K m cAMP-and cGMP-PDEs) were slightly higher in the pellet than in the supernatant after ultracentrifugation (100000 g ). Activity of the low K m PDEs was significantly reduced while that of high K m PDEs was not affected by known inhibitors of PDE. In both normal and RCS rat PE low K m PDEs required calcium and magnesium ions for optimal activity while the high K m PDEs required neither. In homogenates of cultured RCS rat pigment epithelium (PE), the kinetic parameters for cAMP-and cGMP-PDEs were comparable to normal, with the exception of the K m value of the low K m cGMP-PDE. This K m value was two-fold higher in the RCS compared with the normal (indicative of a reduced affinity for cGMP). It remains to be determined if the reduced affinity for cGMP in the RCS PE is related to the genetic defect which is expressed as a deficiency in the phagocytosis of outer segments by these cells. |
| Databáze: | OpenAIRE |
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