Regional and Subcellular Distribution in Mammalian Brain of the Enzymes Producing Adenosine

: The activities of 5′-nucleotidase, 2′-nucleotid-ase, alkaline phosphatase, and acid phosphatase were measured in rat and autopsied human brains. The four phosphatases in the rat brain showed little change in activity after death. The activities of adenosine-producing enzymes were compared in various parts of rat and human brains. When phosphatase activity was measured at pH 7.5, 5′-nucleotidase showed the highest activity in the most parts of the brain. The activity of 2′-nucleotidase and that of nonspecific phosphatase were almost the same at pH 7.5. However, higher phosphatase activity was observed in all parts of the brain when nonspecific phosphatase activity was measured at pH 10.0 or 5.5. High specific activity of 5′-nucleotidase in the brain was detected in the membranous components, especially in the synaptic membranes. The activity of 2′-nucleotidase was distributed in the soluble and synaptosomal fractions. The highest activity of both alkaline and acid phosphatases was recovered in the crude mitochondrial fraction, with the highest specific activity in the microsomal fraction. Phosphatase activity was distributed widely in the rat brain. The activity of 5′-nucleotidase was high in the medulla oblongata, thalamus, and hippocampus, but low in the peripheral nerve, spinal cord, and occipital lobe. The activity of 2′-nucleotidase was high in the vermis and frontal lobe. The highest acid and alkaline phosphatase activities were detected in the frontal lobe and in the olfactory bulb, respectively. The distribution of the four phosphatases in the autopsied human brain was similar to that in the rat brain. The highest 5′-nucleotidase activity was observed in the temporal lobe and thalamus. High activity of 2′-nucleotidase was found in the basal ganglia, substantia nigra, and cortical motor area. Alkaline phosphatase was enriched in the temporal cortex, parietal cortex, and amygdala, and low in the white matter. High acid phosphatase activity was detected in the insula and cerebellar cortex.