Activities of cell‐wall‐degrading enzymes produced by Pestalotiopsis guepinii

Abstract

Pestalotiopsis guepinii is a pathogenic fungus that causes grey blight on Camellia pitardii. In this study, we investigated the enzyme activity and kinetics of these cell‐wall‐degrading enzymes (CWDEs) produced by Pestalotiopsis guepinii in both C. pitardii leaves and culture medium. Our enzyme activity experiments revealed that the activities of xylanase, pectin methyl‐galacturonase (PMG), β‐1,4‐endoglucanase (Cx), and β‐glucosidase were high in both C. pitardii leaves and culture medium. These enzymes played a significant role in the pathogenic process. However, the activity of laccase was found to be very low and had a minor impact on the pathogenic process. Furthermore, our enzyme dynamics experiments demonstrated that the optimal reaction temperature for PMG and Cx was 50°C, while for β‐glucosidase and xylanase, it was 60°C. The optimal reaction pH for Cx, β‐glucosidase, and xylanase was 5.0, whereas for PMG, it ranged from 5.0 to 6.0. This indicates that these four enzymes prefer acidic conditions. Moreover, we observed that the activities of Cx, PMG, and xylanase decreased with increasing reaction time. On the other hand, the activity of β‐glucosidase initially increased sharply and then decreased slowly. The maximum reaction rates of the four cell‐wall‐degrading enzymes were ranked as follows: xylanase > PMG > β‐glucosidase > Cx. Additionally, the affinities of these enzymes with substrates were ranked as follows: PMG < Cx < xylanase < β‐glucosidase.