| |
[摘要]：Trichoderma harzianum ETS 323 secretes two glucanases, a 23.5 kDa endoglucanase (EG Th1) and a 61 kDa exoglucanase (ExG Th1). They were identified by their hydrolysis products and were purified to homogeneity. The optimal temperature and pH for both EG Th1 (7.3-fold purification, 5.0% yield) and ExG Th1 (33.7-fold purification, 0.15% yield) were 50 degrees C and pH 4.5, respectively. The kinetic parameters of EG Th1 (K-m = 23 mg mL(-1), V-max = 294 mu M min(-1), specific activity = 7.4 U mg(-1)) and ExG Th1 (K-m = 85 mg mL(-1), V-max = 385 mu M min(-1), specific activity = 24.6 U mg(-1)) toward carboxymethyl cellulose were determined. Both enzymes favored CMC and maintained 100% activity for 10 days at 38 degrees C. KCl, MgCl2, HgCl2, and FeCl3 showed approximately 30% inhibition against EG Th1 but not ExG Th1. They catalyzed transglycosylation of glucose in the presence of cellobiose, but ExG Th1 exhibited better activity and higher product diversity. |
|
