Studies on the structure of carbohydrate moiety in ovoimucin.

卵粘蛋白是蛋清的一种糖蛋白组分，其特点是分子量高，对蛋清的粘性有贡献。对鸡蛋厚蛋白和薄蛋白中chalaza和ovomucin的电泳分析、分离和表征进行了研究。chalaza和ovomucin由三种分子量估计为150,000、220,000和400,000道尔顿的组分组成，分别命名为< α >1、< α >2和< β >。在SDS和2-巯基乙醇的存在下，通过凝胶过滤将它们分离成低碳水化合物（< α >和< α >2混合物）和富碳水化合物（< β >）组分。除了甘露糖外，< β >-组分所含的碳水化合物浓度远高于< α >-组分。碳水化合物的总含量约为50%，而< α >-组分的含量约为11%。< α >-卵磷脂中的碳水化合物链被认为是天冬酰胺结合的n -糖苷型，而< β >-卵磷脂中的碳水化合物链被认为是与丝氨酸或苏氨酸连接的o -糖苷型。收集< β >-卵泡蛋白，用蛋白酶水解。碱性硼水处理释放了与糖肽相连的碳水化合物链。采用DEAE-Sephadex离子交换色谱分离得到三种酸性低聚糖。采用气相色谱法分析碳水化合物组成，然后用直接质谱法对过甲基化低聚糖进行序列分析，对部分甲基化衍生物进行气相色谱-质谱分析，并用^<13>C-NMR对异位物进行分析。所鉴定的化学结构为Gal-< β >-1-3- galnac -6- so_3h, NANA-< α >-2- 3gal -< β >-1-3- galnac -6- so_3h, NANA-< α >-2-3-Gal-< β >-1-3- 3-[NANA-< α >-2-3-]- galnac。

Ovomucin is a glycoprotein fraction of egg white characterized by high molecular weight and a contributor to the viscous property of egg white. A study was made on the electrophoretic analysis, fractionation and characterization of chalaza, and ovomucin from thick and thin albumen of the hen's egg. The chalaza and ovomucin were confirmed to be composed of three components which the molecular weights were estimated to be 150,000, 220,000 and 400,000 daltons, and named <alpha>1, <alpha>2 and <beta> respectively. They were fractionated into carbohydrate poor (<alpha>1 and <alpha>2 mixture) and rich (<beta>) components by gel filtration in the presence of SDS and 2-mercaptoethanol. The <beta>-component contains much higher concentrations of carbohydrates than <alpha>-component, except for mannose. The total content of carbohydrate amount to about 50 %, whereas that of <alpha>-component is about 11 %. The carbohydrate chain in <alpha>-ovomucin was considered asparagine-binding N-glycosidic type, whereas that in the <beta>-ovomucin is O-grycosidic type linked to serine or threonine.The <beta>-ovomucin was collected and hydrolyzed by proteinases. The carbohydrate chains linked to the glycopeptide were released by alkaline borohydrate treatment. Three acidic oligosaccharides were obtained by fractionation with DEAE-Sephadex ion exchange chromatography. Carbohydrate compositions were analyzed by gas chromatography, and followed by sequence analysis with direct MS of the permethylated oligosaccharides, GC-MS analysis of pertially methylated derivatives and by anomer analysis with ^<13>C-NMR. The chemical structures identified were Gal-<beta>-1-3-GalNAc-6-SO_3H, NANA-<alpha>-2-3Gal-<beta>-1-3-GalNAc-6-SO_3H, and NANA-<alpha>-2-3-Gal-<beta>-1-3-[NANA-<alpha>-2-3-]-GalNAc.