[Effect of straw apoplast protein on cellulase activity]

We studied the alteration of the maize straw apoplast proteins in the process of preservation, and analyzed the effects of apoplast proteins on Penicillum expansum cellulase activities. The results show that: the extractable apoplast proteins are gradually decreased during the preservation of maize straw. Meanwhile, their synergistic effects on P. expensum cellulose are also attenuated. The apoplast proteins extracted from fresh maize straw possess endogenous EG activities, which is unstable and completely vanished after 6 months preservation. The apoplast proteins from the preserved straw exhibit significant synergistic effect on FPA, cotton lyase and beta-glucosidase. The maximal synergistic values are 95.32%, 102.06% and 96.6%, respectively. But interestingly, they inhibit the CMCase activity (max. 49.52%). Apoplast proteins show distinctive synergy with betaG and EG, but have no effect on CBH activity. After eliminating the effect of endogenous EG, the apoplast proteins from fresh maize straw have enhanced synergistic or inhibiting effects on FPA, Cotton lyase, betaG and CMCase than those extracted from the preserved straw. Based on our observation, the apoplast proteins play important roles in regulating the cellulase activities. The detailed analysis of the related mechanisms will greatly benefit the studies of the natural biomaterials hydrolysis.