抄録
The carbohydrate portions of β-galactosidase from Aspergillus oryzae were found to be composed of two types of sugar chains. They were released equally well with endo β-N-acetylglucosaminidase H, but were distinct in their chain length. The long sugar chains (fraction I), corresponding to 4% of the total carbohydrate chains, were composed of galactomannan-type oligosaccharides, which consisted of man-nose, galactose, glucose, and glucosamine in the molar ratios of 30.0, 16.4, 1.4, and 2.1 per mol of aspartic acid, respectively. The short sugar chains (fraction II), corresponding to 96% of the total carbohydrate chains, consisted of mannose, galactose, glucose, and glucosamine in the molar ratios of 9.4, 0.6, 0.3, and 1.7 per mol of aspartic acid, respectively. Both types of sugar chains were fractionated into neutral and acidic subfractions. The neutral subfraction of fraction I (I-N), corresponding to 1% of the total carbohydrate chains, was very heterogeneous in length and was resistant to digestion with a-mannosidase and β-galactosidase. The neutral subfraction of fraction II (II-N), corresponding to 91 % of the total car-bohydrate, was composed of a mixture of oligosaccharides with oligomanneoside chains (Mann GlcNAcol). The major components were similar to high mannose-type oligosaccharides of mammalian origin in their composition and size (n=5-9). However, digestion of II-N with α1, 2-mannosidase produced considerable amounts of Man6G1cNAcol, an unusual product in the case of high mannose-type oligosaccharides of mammalian origin, in addition to the common one, Man5G1cNAcol. The following structure is proposed for Man6G1cNAcol:
The acidic subfraction of fraction I, corresponding to 1.3 % of the total carbohydrate chains, contained phosphate in mono- and diester linkages, whereas the acidic subfraction of fraction II, corresponding to 3 % of the total carbohydrate chains, contained phosphate only in monoester linkages.
