Biochemical characterization of postsynaptically localized cyclic nucleotide phosphodiesterase.

This study demonstrates the postsynaptic localization of one of the isozymes of cyclic nucleotide phosphodiesterase (PDE) activity at asymmetrical, axospinous terminals in the rat corpus striatum and neocortex. Characterization of this enzymatic activity demonstrates that the PDE form surviving aldehyde fixation for electron cytochemistry can be considered to preferentially hydrolyze cyclic 3'5'-guanosine monophosphate, and it requires calcium and a heat-stable calcium-dependent regulator protein (CDR) for full hydrolytic activity. Ion exchange chromatographic analysis of extracts of corresponding unfixed brain regions demonstrates that only one enzyme activity peak exhibits similar aldehyde resistance and calcium and regulator protein activatibility.