色氨酸残基在双功能酶CCBE中的作用  

Effect of Tryptophan Residues in Cellulase-Chitosanase Bifunctional Enzyme from Trichoderma viride Cellulase

作　　者：刘靖[1] 夏文水[1] 

机构地区：[1]江南大学食品科学与安全教育部重点实验室

出　　处：《食品科学》2007年第9期425-429,共5页Food Science

基　　金：国家自然科学基金资助项目(20576104)

摘　　要：应用化学修饰剂NBS对从绿色木霉生产的纤维素酶中分离出的既具有壳聚糖酶活性又具有纤维素酶活性的单一组分(简称双功能酶CCBE)进行了修饰。结果表明,CCBE的壳聚酶活性中心需一分子色氨酸残基,CMCase活性中心需两分子色氨酸残基;底物保护作用及酶解动力学研究表明,CCBE的壳聚酶活性中心及CMCase活性中心的一分子的色氨酸残基位于底物结合部位,而CMCase活性中另一分子色氨酸残基位于催化结构中心。The bifunctional enzyme（CCBE）, which was purified from Trichoderma viride cellulase with cellulase-chitosanase activities, was modified by N-bromossuccinimide（NBS）. The results indicated that NBS could both inactivate its cellulase activity and chitosanase activity. The kinetic analysis revealed that two tryptophan（Trp） residues were essential for its cellulase activity and one Trp residue for its chitosanase activity. 93% protection by 0.5% chitosan against inactivation by NBS, compared with 60% protection by 0.5% CMC, showed that one Trp residue was at the CCBE substrate binding site for both of its cellulase activity and chitosanase activity, and one Trp residue was at the catalytic site of its cellulase activity. Km increase of NBS modified CCBE was detected. These information confirmed above.

关 键 词：双功能酶 色氨酸残基 化学修饰 

分 类 号：Q517[生物学—生物化学]