Characterization of Cyclic Nucleotide Phosphodiesterases of Rat Tissues

Abstract Cyclic nucleotide phosphodiesterase has been prepared from the liver, skeletal muscle, heart muscle, kidney, epididymal fat pad, and brain cortex of the rat. Kinetic analysis indicated that all of these tissues, with the exception of liver exhibit complex behavior indicative of multiple enzymatic activities. The phosphodiesterase activities of brain cortex, kidney, and adipose tissue have been resolved on Bio-Gel A-1.5m gel filtration columns into three fractions. These are an excluded fraction, a high molecular weight fraction in which the enzymatic affinity for cyclic guanosine 3',5'-monophosphate is greater than that for cyclic adenosine 3',5'-monophosphate, and a lower molecular weight fraction with a high affinity for cyclic adenosine 3',5'-monophosphate. The lower molecular weight enzyme appears to be negatively cooperative. The muscle preparations have little, if any, of the excluded fraction which in kidney, adipose tissue, and brain has kinetic behavior similar to that of the lower molecular weight enzyme. Liver has no detectable phosphodiesterase activity in any except the intermediate fraction which has a molecular weight of approximately 400,000. This enzymatic activity has been purified 88-fold by centrifugation, ammonium sulfate fractionation, and gel filtration. The potential for metabolic control through regulation of cyclic nucleotide phosphodiesterase is discussed in view of the existence of at least two distinct enzymatic activities in all of tissues studied except the liver.