Analysis of the three-dimensional structure of AEXynM. (A) The three-dimensional structure of AEXynM predicted by MODELLER 9.9. Two invariant catalytic residues, Glu89 and Glu180, reside at the center of an active region. The amino acid residues (Cys5, Pro9, and His14) mainly responsible for the high thermostability of AEXynM are located in β-strands A1 and B1, respectively. (B) One disulfide bridge (Cys5-Cys32) is illustrated in the locally magnified three-dimensional structure. (C) The residues (Pro9, Phe21, and Trp22) represented with spheres compose a hydrophobic interaction cluster. The hydrogen bond between His14 and Phe17 is illustrated with a dashed line.