Effect of Straw Apoplast Protein on Cellulase Activity

The alteration of the maize straw apoplast proteins involved in the process of preservation was studied and the effects of the apoplast proteins on Penicillum expansum cellulase activities were analyzed. The results obtained by the study and the analysis showed a gradual decrease in the extractable apoplast proteins that occurred during the preservation of the maize straw. Meanwhile, their synergistic effects on P. expensum cellulase were also attenuated. The apoplast proteins that were extracted from the fresh maize straw possess endogenous EG activities but these were unstable and completely disappeared after 6 months of preservation. The apoplast proteins that were extracted from the preserved straw exhibited a large amount of synergistic effects on FPA, cotton lyase, and β-glucosidase. The maximum synergistic values were 95.32 %, 102.06 %, and 96.6 %, respectively. They inhibit the CMCase activity at a maximum value of 49.52 %. The apoplast proteins show distinctive synergistic effects with βG and EG, but have no effects on the CBH activity. When the synergistic effects on endogenous EG were eliminated, the apoplast proteins extracted from fresh maize straw showed more enhanced synergistic or inhibiting effects on FPA, cotton lyase, βG, and CMCase than in the case where the apoplast proteins extracted from the preserved straw. On the basis of the observation, the extracted apoplast proteins play important roles in the regulation of cellulase activities. The detailed analysis of the related mechanisms will greatly benefit the studies of natural biomaterial hydrolysis.