Membrane anchoring and surface distribution of glycohydrolases of human erythrocyte membranes

The membrane anchoring of the following glycohydrolases of human erythrocyt e plasma membranes was investigated: alpha- and beta-D-glucosidase, alpha- and beta-D-galactosidase, beta-D-glucuronidase, N-acetyl-beta-D-glucosamini dase, alpha-D-mannosidase, and alpha-L-fucosidase. Optimized fluorimetric m ethods for the assay of these enzymes were set up. Treatment of the ghost p reparation with 1.0 mol/l (optimal concentration) NaCl caused release rangi ng from 4.2% of alpha-D-glucosidase to 70% of beta-D-galactosidase; treatme nt with 0.4% (optimal concentration) Triton X-100 liberated 5.1% of beta-D- galactosidase to 89% of alpha-D-glucosidase; treatment with 1.75% (optimal concentration) octylglucoside yielded solubilization from 6.3%, of beta-D-g alactosidase to 85% of alpha-D-glucosidase. Treatment with phosphoinositide -specific phospholipase C caused no liberation of any of the studied glycoh ydrolases. These results are consistent with the notion that the above glyc ohydrolases are differently anchored or associated with the erythrocyte pla sma membrane, and provide the methodological basis for inspecting the occur rence of these enzymes in different membrane microdomains. (C) 2000 Federat ion of European Biochemical Societies.