MAXIMUM ACTIVITIES, PROPERTIES AND DISTRIBUTION OF 5' NUCLEOTIDASE, ADENOSINE KINASE AND ADENOSINE-DEAMINASE IN RAT AND HUMAN-BRAIN

The maximum activities of 5'' nucleotidase, adenosine kinase and adenosine deaminase were measured in several areas of rat and human brain. There is no major difference between the activities of nucleotidase and kinase between rat and human brain, but the activity of deaminase is considerably higher in human brain. The activities of all these enzymes are similar in 3 areas of rat brain and 9 areas of human brain, except for the hind brain of the human, which has a low activity of adenosine deaminase. This variation may indicate the existence of different steady-state concentrations of adenosine in certain areas of the brain. Subcellular fractionation of different areas of rat brain showed that, whereas adenosine kinase and deaminase activities were located mainly in the soluble fractions, 5'' nucleotidase was present in all subcellular fractions (i.e., membrane, synaptosomal, mitochondrial and soluble). There was no major localization within the synaptosomal fraction. The regulation of the activities of these enzymes apparently is not dependent upon changes within a specific compartment (e.g., synaptosomes) in the brain.