Glycosidases in the Nervous System

A modification of the analytical method employing the appropriate 4-methylumbelliferyl-β-d-glycoside as substrate and measuring the fluorescence of the 4-methylumbelliferone freed by hydrolysis permitted the measurement of β-galactosidase, β-glucuronidase, and β-glucosidase in individual anterior horn cell bodies, in individual dorsal ganglion cell bodies, and in pieces of anterior horn neuropil approximately equivalent in weight (0.01 µg) to one individual cell body. Incubation for 18 hours was necessary to measure the two latter enzymes in a single cell, whereas it was necessary to incubate β-galactosidase for only 4 hours because of its higher activity. When incubation was for 18 hours, the fall-off of activity for β-glucuronidase was negligible, but for β-galactosidase the fall-off in activity was about 57%. The results for β-glucosidase were somewhat anomalous in that the fall-off activity with time for cerebellar molecular layer was very different (over 10-fold) from the fall-off for nerve cells, neuropil, or other cerebellar layers (average of 2.5-fold). The concentration of each of these three enzymes was extremely rich in nerve cell bodies when compared with the neuropil in the cord, varying from 14- to 27-fold for dorsal ganglion cell bodies, and from 8- to 10-fold for anterior horn cell bodies. These results contrast strikingly with those found by others and ourselves in which levels of carbohydrate-metabolizing enzymes, glutamate-metabolizing enzymes, and a dipeptidase in nerve cell bodies were found to be equal to or lower than the levels in neuropil and in other parts of the nervous system.