of nerve cells: A developmental study of two molecular components

1. 1. The development of the lysosomal hydrolase was examined in bulk-isolated nerve cell bodies of rat cerebral cortex. Several properties of the enzyme and of two of its molecular components were compared, among them their ease of solubilization, their relative abundance, their heat lability and their behavior on density gradients of sucrose.2. 2. Repeated freezing-thawing of neuronal particulates in 0.20 M sucrose-0.1 M KCl followed by centrifugation at moderate rather than high speeds resulted in the solubilization of upward of 50% of the glucosaminidase, irrespective of neuronal age.3. 3. Although the solubilization of was dependent on the concentration (mg of protein/ml) of the suspension subjected to freezing-thawing, it was always more effective with the enzyme from the 8- and 18-day-old than with that from the 3- and 5-day-old neurons.4. 4. Centrifugation of the solubilized neuronal on linear density gradients of sucrose resulted, at all ages, in the complete resolution of two activity components a heavy and a light one, H and L respectively. As routinely isolated, the ratio of component L to component H in the neurons of the cerebral cortex was always > 1.0 while, in the cerebellar neurons, values 5. 5. The qualitative and quantitative gradient profiles of activity were highly sensitive to pH. Thus, lowering of the pH of frozen thawed supernatants to 5.4 and below prior to density gradient centrifugation resulted in the virtual disappearance of component H, while adjustment of the pH to 5.6 resulted in L/H ratios 6. 6. About 50% of the activity of component L was lost, irrespective of age, by heating for 20 min at 50 [deg]C and at a pH of 4.1. The heat sensitivity of component H was no greater, except at 5 days, when about 90% of its activity was lost under the same conditions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33848/1/0000106.pd