β-HEXOSAMINIDASES IN THE NERVOUS SYSTEM: THE QUANTITATIVE HISTOCHEMISTRY OF β-GLUCOSAMINIDASE AND β-GALACTOSAMINIDASE IN THE CEREBELLAR CORTEX AND SUBJACENT WHITE MATTER

A modification of an existing fluorimetric method for the assay of β-glucosaminidase and β-galactosaminidase, based upon the hydrolysis of the corresponding 4-methylumbelliferyl glycosaminides, is described. The method is simple and convenient; its sensitivity is 3 x 10–8 M for the assay of β-glucosaminidase and 1 x 10–8 M for β-galactosaminidase. The results obtained on brain homogenates and dissected sections of cerebellar cortex and subjacent white matter of rat, rabbit and monkey were found to be similar to those obtained with the standard colorimetric procedures using p-nitrophenyl substrates. In each species, in each layer of cerebellar cortex and subjacent white matter, there were only minimal differences in the ratios of β-glucosaminidase to β-galactosaminidase activity, suggesting that a single enzyme possesses both activities. β-Glucosaminidase and β-galactosaminidase in the cerebellum were most active in the cellular granular layer, suggesting an association of β-hexosaminidase activity with neuronal cell bodies as has been found with other lysomal enzymes.