Pazur J H, Tominaga Y, Forsberg L S, Simpson D L
Carbohydr Res. 1980 Sep 8;84(1):103-14. doi: 10.1016/s0008-6215(00)85434-8.
Glucoamylase, (1 leads to 4)(1 leads to 6)-alpha-D-glucan glucohydrolase (EC 3.2.1.3), hydrolyzes starch and glycogen completely to D-glucose and is used industrially in the manufacture of D-glucose from starch. The enzyme is elaborated by many types of fungi and occurs in two isoenzymic forms (glucoamylase I and glucoamylase II) in extracts from certain fungi. The isoenzymes from Aspergillus niger are glycoenzymes containing D-mannose, D-glucose, and D-galactose as integral structural components. New data from experiments on reductive alkaline beta-elimination and from methylation analyses show that the carbohydrate chains of glucoamylase I are linked O-glycosidically from D-mannose residues to L-serine or L-threonine residues of the protein moiety. In this enzyme, the carbohydrate residues are present as 20 single D-mannose residues, 11 disaccharides components having the structure 2-O-D-mannopyranosyl-D-mannose, 8 trisaccharides, and 5 tetrasaccharides composed of various combinations of D-mannose, D-glucose, and D-galactose residues joined by (1 leads to 3) and (1 leads to 6) glycosidic linkages. Such an array of carbohydrate chains in a glycoprotein is unusual, and may account for some of the unique properties exhibited by glucoamylase.
葡糖淀粉酶，（1→4）（1→6）-α-D-葡聚糖葡糖水解酶（EC 3.2.1.3），可将淀粉和糖原完全水解为D-葡萄糖，在工业上用于从淀粉制造D-葡萄糖。该酶由多种真菌产生，在某些真菌的提取物中以两种同工酶形式（葡糖淀粉酶I和葡糖淀粉酶II）存在。黑曲霉的同工酶是糖酶，含有D-甘露糖、D-葡萄糖和D-半乳糖作为必需的结构成分。还原碱性β-消除实验和甲基化分析的新数据表明，葡糖淀粉酶I的碳水化合物链通过O-糖苷键从D-甘露糖残基连接到蛋白质部分的L-丝氨酸或L-苏氨酸残基。在这种酶中，碳水化合物残基以20个单个D-甘露糖残基、11个具有2-O-D-甘露吡喃糖基-D-甘露糖结构的二糖成分、8个三糖和5个由D-甘露糖、D-葡萄糖和D-半乳糖残基通过（1→3）和（1→6）糖苷键连接的各种组合组成的四糖形式存在。糖蛋白中如此排列的碳水化合物链并不常见，可能是葡糖淀粉酶表现出一些独特性质的原因之一。
