Stability of enzymes of lysosomal origin in human cerebrospinal fluid

The optimal assay conditions and the stability of the following enzymes of lysosomal origin in human cerebrospinal fluid (CSF) were studied: acid phosphatase, beta-D-N-acetylglucosaminidase, alpha-D-galactosidase, beta-D-galactosidase, alpha-D-glucosidase, beta-D-glucosidase, alpha-L-fucosidase, alpha-D-mannosidase, beta-D-glucuronidase. The microsomal alpha-D-mannosidase, pH 5.7, was used as a reference non-lysosomal glycohydrolase. All the examined enzymes, with the only exception of beta-D-glucuronidase, underwent a more or less rapid loss of activity upon CSF storage in the temperature range from 37 degrees C to -80 degrees C. Storage in liquid nitrogen (-196 degrees C) was the only condition in which full activity for all tested enzymes was maintained for at least 15 days. Addition of human serum albumin to CSF, immediately after withdrawal, had a double effect in favouring enzyme stabilization and causing enzyme activation in some cases, and enzyme inhibition in others. Using conditions warranting enzyme stability the fluorimetric methods for lysosomal enzymes determination in cerebrospinal fluid appear to be highly reproducible (CV less than 5%) and simple enough for routine use.