Biochemical properties of Glu-SH3 as a family 13 glycoside hydrolase with remarkable substrate specificity for trehalose: Implications to sequence-based classification of CAZymes

A glycoside hydrolase 30 protein BpXynC of Bacillus paralicheniformis NMSW12 recognized as A MAMP triggers plant immunity response

Bacillus spp. has been widely used as a biocontrol agent to control plant diseases. However, little is known about mechanisms of the protein MAMP secreted by Bacillus spp. Herein, our study reported a glycoside hydrolase family 30 (GH30) protein, BpXynC, produced by the biocontrol bacteria Bacillus paralicheniformis NMSW12, that can induce cell death in several plant species. The results revealed that the recombinant protein triggers cell death in Nicotiana benthamiana in a BAK1-dependent manner and elicits an early defense response, including ROS burst, activation of MAPK cascades, and upregulation of plant immunity marker genes. BpXynC was also found to be a glucuronoxylanase that exhibits hydrolysis activity on xlyan. Two mutants of BpXynC which lost the glucuronoxylanase activity still retained the elicitor activity. The qRT-PCR results of defense-related genes showed that BpXynC induces plant immunity responses via an SA-mediated pathway. BpXynC and its mutants could induce resistance in N. benthamiana against infection by Sclerotinia sclerotiorum and tobacco mosaic virus (TMV). Furthermore, BpXynC-treated tomato fruits exhibited strong resistance to the infection of Phytophthora capsica. Overall, our study revealed that GH30 protein BpXynC can induce plant immunity response as MAMP, which can be further applied as a biopesticide to control plant diseases.

Analysis of the structure-function relationship of alpha amylase complexed with polyacrylic acid

Alpha-amylase is frequently used in technologies that require its immobilization, stabilization or encapsulation. Polyacrylic acid is a very suitable polymer for these purposes because it can bind to enzymes and then be released under certain conditions without altering the functional capacity of enzymes. The consequences produced by polyacrylic acid on alpha-amylase structure and function have been investigated through various techniques. Calorimetric measurements allowed examining the nature of the binding reaction, stoichiometry and affinity, while spectroscopic techniques provided additional information about functional and structural perturbations of the enzyme. Isothermal titration calorimetry (ITC) revealed a mixed interaction and a binding model with a large number of molecules of protein per molecule of polyacrylic acid. One the one hand circular dichroism (CD) spectroscopy showed that alpha-amylase loses its secondary structure in the presence of increasing concentrations of polyacrylic acid, while it is stabilized by the polyelectrolyte at low pH. On the other hand, fluorescence spectra revealed that the three-dimensional enzyme structure was not affected in the microenvironment of tryptophan residues. Differential scanning calorimetry (DSC) thermograms showed that only one domain of alpha-amylase is affected in its conformational stability by the polymer. The unfolding process proved to be partially reversible. Finally, the enzyme retained more than 90 % of its catalytic activity even in excess of the polymer.