海枣曲霉木聚糖酶Ⅲ糖组成及糖肽结合键研究

SUGAR COMPOSITION AND GLYCOSYL BONDS OF XYLANASE Ⅲ FROM ASPERGILLUS PHOENICIS

海枣曲霉木聚糖酶Ⅲ经PAGE和SDS-PAGE后用Schiff’s试剂染色证明为糖蛋白。经硅胶薄层层析和毛细管气相色谱测定,每分子酶约含4个葡萄糖和1个甘露糖残基。 木聚糖酶Ⅲ经β-消除反应后在241nm处出现一个新的吸收峰。在N_2保护下用含NaBH_4的NaOH溶液处理后,其Ser和Thr减少,相对应丙氨酸增加,并出现α-氨基丁酸。估测酶分户中存在约3个O-糖苷键,糖残墓通过O-糖苷键连接于肽链中丝氨酸或苏氨酸上。

Xylanase Ⅲ from Aspergillus phoenicis was identified as glycoprotein on PAGE and SDS-PAGE stained with Schiff's reagent. The carbohydrate composition of the enzyme was analyzed by silica gel thin layer and gas capillary chromatographies. It contained about 4 glucose residues and 1 mannose. Xylanase Ⅲ after β- elimination reaction yielded an absorption peak at 241nm. With the treatment of alkali sodium borohydride under the protection of N2, the serine and threonine residues decreased, while alanine increased and α- amino - n - butyric acid appeared. It was suggested that xylanase Ⅲ had about 3 O - glycosyl bonds and the sugar residues are linked to serine and threonine of peptide chain through O - glycosyl bonds.