Lee S B, Kim I H, Ryu D D, Taguchi H
The Korea Advanced Institute of Science, P.O. Box 150, Chung Ryang Ri, Seoul, Korea.
Biotechnol Bioeng. 1983 Jan;25(1):33-51. doi: 10.1002/bit.260250105.
The effects of structural properties and their changes during cellulose hydrolysis on the enzymatic hydrolysis rate have been studied from the reaction mechanism point of view. Important findings are the following: (1) The crystallinity index (CrI) of partially crystalline cellulose increases as the hydrolysis reaction proceeds, and a significant slowing down of the reaction rate during the enzymatic hydrolysis is, in large part, attributable to this structural change of cellulose substrate. (2) The crystallinity of completely disordered cellulose, like phosphoric-acid-treated cellulose, does not change significantly, and a relatively high hydrolysis rate is maintained during hydrolysis. (3) The specific surface area (SSA) of partially crystalline cellulose decreases significantly during enzymatic hydrolysis while the change in SSA of regenerated cellulose is found to be negligible. (4) The value of degree of polymerization (DP) of highly ordered crystalline cellulose remains practically constant whereas the change in DP of disordered regenerated cellulose is found to be very significant. (5) Combination of these structural effects as well as cellulase adsorption, product inhibition, and cellulase deactivation all have important influence on the rate of cellulase reaction during cellulose hydrolysis. More experimental evidence for a two-phase model, which is based on degradation of cellulose by simultaneous actions of cellulase complex on the crystalline and amorphous phases, has been obtained. Based on experimental results from this study and other results accumulated, the mode of cellulase action and a possible reaction mechanism are proposed.
从反应机理的角度研究了纤维素水解过程中结构性质及其变化对酶水解速率的影响。重要发现如下：(1)随着水解反应的进行，部分结晶纤维素的结晶度指数（CrI）增加，酶水解过程中反应速率的显著减慢在很大程度上归因于纤维素底物的这种结构变化。(2)完全无序的纤维素（如磷酸处理的纤维素）的结晶度没有显著变化，水解过程中保持相对较高的水解速率。(3)部分结晶纤维素的比表面积（SSA）在酶水解过程中显著降低，而再生纤维素的SSA变化可忽略不计。(4)高度有序的结晶纤维素的聚合度（DP）值实际上保持不变，而无序再生纤维素的DP变化非常显著。(5)这些结构效应以及纤维素酶吸附、产物抑制和纤维素酶失活的综合作用对纤维素水解过程中纤维素酶反应的速率都有重要影响。基于纤维素酶复合物对结晶相和无定形相同时作用降解纤维素的两相模型，获得了更多实验证据。基于本研究的实验结果和积累的其他结果，提出了纤维素酶的作用模式和可能的反应机制。
