β-Hexosaminidase, α-D-mannosidase, and β-mannosidase expression in serum from patients with carbohydrate-deficient glycoprotein syndrome type I

The activity of β-hexosaminidase, determined with 4-methylumbelliferyl-β-N-acetylglucopyranoside substrate, and of β-D-mannosidase was significantly higher in the serum of patients with carbohydrate-deficient glycoprotein (CDG) syndrome type IA (phosphomannomutase deficiency) than in controls. No significant differences were observed in the activity of β-hexosaminidase, determined using 4-methylumbelliferyl-β-N-acetylglucopyranoside-6-sulphate as substrate, and the activity of α-D-mannosidase. Using DEAE-cellulose chromatography, a greater amount of hexosaminidase B than hexosaminidase A was detected in CDG serum. In CDG serum, hexosaminidase A was eluted in a more basic position in the salt gradient. An isoenzyme of α-D-mannosidase and β-D-mannosidase was identified in control and CDG sera. α-D-Mannosidase isoenzyme was eluted in a slightly more basic position in CDG serum than in control serum, whereas β-D-mannosidase isoenzyme was eluted in the same position. (C) 2000 Elsevier Science B.V.