Purification and partial characterization of the carbohydrate structure of lysosomal N-acetyl-beta-D-hexosaminidases from bovine brain

1. The lysosomal forms A and B, and an intermediate form I of N-acetyl-beta-D-hexosaminidase (EC 3.2.1.30) were isolated from bovine brain, resulting in the following purification factors and specific activities: hexosaminidase A 20255, 103 U mg-1; hexosaminidase B 34715, 134 U mg-1; hexosaminidase I 15241, 78 U mg-1. 2. The molecular weights of the polypeptide chains were identical for each isoenzyme: two bands of 50 and 53 k daltons were found. 3. Carbohydrate analysis showed the presence of mannose, galactose, N-acetylglucosamine and sialic acid. This composition, and the absence of N-acetylgalactosamine, indicated that only N-glycosidically linked oligosaccharide chains are present. 4. The amino-acid composition showed no substantial differences for the three isoenzymes.