拟康氏木霉S—38中纤维素酶的动力学研究

The mechanism of fungal cellulase action from Trichoderma pseudoningii S-38 by using kinetic analysis during isothermcondition for pH effect

采用动力学的方法研究了等温条件下PH值变化对拟康氏木霉中两个外切酶（CBHⅠ，CBHⅠ）和一个内切酶（EGⅠ）动力学参数的影响。结果表明，EGⅠ游离酶的pKe1及pKe2分别为4．4和5．7，EGⅠ酶—底物复合物的pKes1及pKes2分别为3．6和5．5；外切酶CBHⅠ的pKe1及pKe2分别为3．6和6．3，pKes1及pKes2分别为3．4和6．0；外切酶CBHⅡ的pKe1及pKe2分别为3．6和6．2，pKes1及pKes2分别为3．4和5．9。这些结果说明纤维素酶中存在两个羧基或一个羧基和一个咪唑基参与酶的催化反应，这种机制和溶菌醇是相似的。

Studies on cellulose hydrolpeis of two cellobiohydrolases and one endoglu-canase were investigated by kinetic method. The pH profile for log VmKm gave the kineticapparent pK Values 3. 6 and 5. 5 for groups in the enzyme-substrate complex and 4. 4 and5. 7 for pKe of groups in either the enzyme of free substrate for endoglucanase. By con-trast in the case of the cellobiohydrolases pKe1=3. 6,pKe2= 6. 3,pKes 1= 3. 4,pKes 2=6. 0 for CBH Ⅰ,and pke1=3. 6,pKe2=6. 1,pKes1=3. 4,pKes2=5. 9 for CBH Ⅱ. Theseresults indicating that the presence of carboxyl groups and (or) a histidine residue at theactive site of cellulase,which were responsible for binding,or for catalysis,or for both,and mechanism of action in cellulase from Trichoderma pseudoningii S-38 is remarkablysimilar to the lysozyme.