Identification and characterization of an acetyl xylan esterase from Aspergillus oryzae.

In this study, we report the identification and characterization of an acetyl xylan esterase, designated as AoAXEC, which was previously annotated as a hypothetical protein encoded by AO090023000158 in the Aspergillus oryzae genomic database. Based on its amino acid sequence, a low sequence identity to known acetyl xylan esterases was observed in the sequence of characterized acetyl xylan esterase. The gene fused with α-factor signal sequence of Saccharomyces cerevisiae instead of the native signal sequence was cloned into a vector, pPICZαC, and expressed successfully in Pichia pastoris as an active extracellular protein. The purified recombinant protein had pH and temperature optima of 7.0 and 50 °C, respectively, and was stable up to 50 °C. The optimal substrate for hydrolysis by the purified recombinant AoAXEC, among a panel of α-naphthyl esters (C2-C16), was α-naphthyl propionate (C3), with an activity of 0.35 ± 0.006 units/mg protein. No significant difference of the K

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