Lysosomal N-acetyl-beta-D-glucosaminidase: interneuronal differences in activity and molecular forms.

The lysosomal N-acetyl-fl-D-glucosaminidase (EC 3.2.1.30) of brain tissue 1~ has been extensively studied in our laboratory 7,15-1s, with particular emphasis on the distinction between its neuronal and glialT,10,19 components. Evidence for two neuron-al components in the immature rat cerebral cortex, each with distinct characteristics, was presented in 1973 (ref. 18). More recently, we demonstrated the presence of similar components 17 in Purkinje cell bodies, bulk-isolated from the immature rat cerebellar cortex 14. It is of interest that several recent reports describing, inter alia, the existence of N-acetyl-fl-D-glucosaminidase C in human brain 2, and the purification of N-acetyl-fl-o-glucosaminidase A from monkey and human brain 1, failed to consider the possibility of differences in cellular origins and hence in the properties of the activities studied. In this communication we describe differences in the distribution of molecular forms of N-acetyl-fl-D-glucosaminidase in the neurons of 3 different rat brain regions: the midbrain, the brain stem and the hypothalamus. We also report on the solubiliza-tion characteristics of N-acetyl-fl-o-glucosaminidase in these and two other brain regions, the striatum and the hippocampus. The results reveal that the different neuronal cell types possess different complements of N-acetyl-fl-o-glucosaminidase activity which, in all likelihood, reflect each cell type's specific performance potential at the lysosomal level. Neuronal perikarya were isolated by the procedure previously used for the isolation of perikarya from the cerebral cortex with no modifications is. Twenty 18-day-old male Sprague-Dawley rats were used in each experiment and perikarya were isolated from 3 brain regions per experiment. The procedure of Glowinski and Iversen 3 was used for the manual dissection of the brain regions. The mean values in grams of the wet weights of 20 brain regions (number of experiments in parenthesis) were: hypothalamus, 0. Previously described proceduresT, is were used for the isolation of a mixed, particulate fraction (Mit, Ly, Mic) enriched in N-acetyl-fl-D-glucosaminidase and for its solubilization by repeated (3 ×) freezing and thawing 18.