Ramírez M, Muñoz M D, Larriba G
Departamento de Microbiología, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain.
Biochim Biophys Acta. 1989 Feb 24;990(2):206-10. doi: 10.1016/s0304-4165(89)80035-2.
The major exoglucanase (1,3-beta-D-glucan glucanohydrolase, EC 3.2.1.39) secreted by Saccharomyces cerevisiae contains protein, mannose and phosphate in a molar ratio of 1:27:1. When digested with endo-beta-N-acetylglucosaminidase H (EC 3.2.1.96) it sequentially released two asparagine-linked oligosaccharide chains. Oligosaccharides were fractionated into a neutral and acidic component, each one accounting for 50% of the total carbohydrate. The neutral oligosaccharide consisted of a mixture of three homologues ranging from GlcNAc-(Man)12 to GlcNAc-(Man)14. The acidic carbohydrate was, in turn, split into two components. The major one (45% of the initial material) contained a phosphodiester bond and released only mannose when subjected to mild acid hydrolysis. From the filtration pattern, it was shown to be a mixture of oligosaccharides ranging from GlcNAc-(Man)11-P to GlcNAC-(Man)13-P. The minor phosphorylated component, which represented the residual carbohydrate (5%), contained a phosphomonoester bond. It was also heterogeneous in size, the several homologues having one mannose less than their counterparts from the phosphodiester oligosaccharide. These results clearly indicate that the addition of an outer chain of carbohydrate is not a requirement for the externalization of yeast glycoproteins.
酿酒酵母分泌的主要外切葡聚糖酶（1,3-β-D-葡聚糖葡聚糖水解酶，EC 3.2.1.39）含有蛋白质、甘露糖和磷酸盐，其摩尔比为1:27:1。用内切β-N-乙酰葡糖胺糖苷酶H（EC 3.2.1.96）消化时，它会依次释放两条天冬酰胺连接的寡糖链。寡糖被分离成中性和酸性组分，每种组分各占总碳水化合物的50%。中性寡糖由三种同系物的混合物组成，范围从GlcNAc-(Man)12到GlcNAc-(Man)14。酸性碳水化合物又被分成两个组分。主要组分（占初始物质的45%）含有一个磷酸二酯键，在温和酸水解时仅释放甘露糖。从过滤模式来看，它是一种寡糖混合物，范围从GlcNAc-(Man)11-P到GlcNAC-(Man)13-P。次要的磷酸化组分占剩余碳水化合物的5%，含有一个磷酸单酯键。其大小也不均一，几种同系物比磷酸二酯寡糖的对应物少一个甘露糖。这些结果清楚地表明，添加碳水化合物外链不是酵母糖蛋白外化的必要条件。
