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CYCLIC NUCLEOTIDE METABOLISM IN ELECTROPLAX OF ELECTROPHORUS ELECTRICUS
Author(s) -
Childers S. R.,
Siegel F. L.
Publication year - 1977
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1977.tb12314.x
Subject(s) - electrophorus , cyclic nucleotide phosphodiesterase , calcium , phosphodiesterase , egta , biochemistry , cyclic nucleotide , chemistry , torpedo , cholinergic , ionophore , biology , enzyme , nucleotide , endocrinology , acetylcholine receptor , receptor , organic chemistry , gene
— In order to describe the regulation of cyclic nucleotide metabolism in a cholinergic tissue, the properties of cyclic nucleotide phosphodiesterase were determined in electroplax of Electrophorus electricus and compared to those of mammalian brain. Electroplax phosphodiesterase was Mg 2+ ‐dependent. localized in the soluble fraction and displayed normal linear Lineweaver‐Burk kinetics ( K m : cyclic AMP. 1.4 μ m ; cyclic GMP, 0.54 μ m ). No low affinity (i.e. high K m ) activity was detected. These results were correlated with comparatively low tissue levels of cyclic AMP (67 pmol/g) and cyclic GMP (3.2 pmol/g). Attempts were made to detect calcium‐dependent phosphodiesterase because of the presence of large amounts of the calcium‐dependent regulator protein (CDR) in electroplax, as this protein has been shown to activate brain phosphodiesterase. Assay with EGTA under a variety of conditions revealed that no calcium‐dependent activity could be detected. Preparation of CDR‐deficient phosphodiesterase also failed to produce calcium‐dependent activity. Assay of phosphodiesterase in other cholinergic tissues revealed calcium‐dependent activity in Electrophorus muscle and rat diaphragm but not in Torpedo electroplax. The results suggest that calcium‐dependent activity is not a significant portion of phosphodiesterase in electroplax and indicate alternate roles for CDR in electric tissue.