alpha-Glucosidase and N-acetyl-beta-D-glucosaminidase isoenzymes in serum

Using different conditions for incubation and fluorometry with 4-methylumbelliferylglycosides as substrates, we demonstrated the presence of acid alpha-glucosidase, "renal" alpha-glucosidase, N-acetyl-beta-D-glucosaminidase A, and N-acetyl-beta-D-glucosaminidase B in freshly drawn normal human serum. The acid alpha-glucosidase enzymatic activity was determined at pH 4.0 in 0.1 mol/L Tris reagent, whereas the renal isoenzyme activity was determined at pH 5.6 in presence of 0.05 mol/L turanose reagent. N-Acetyl-beta-D-glucosaminidases A and B were determined by their different behaviors on heating. The corresponding reference intervals for each enzyme were calculated from results for 40 controls: acid alpha-glucosidase (0.024 +/- 0.010 U/L), renal alpha-glucosidase (0.035 +/- 0.012 U/L), N-acetyl-beta-D-glucosaminidase A (10.2 +/- 2.9 U/L), and N-acetyl-beta-D-glucosaminidase B (4.4 +/- 2.1 U/L).