Characterization of Heterologously Expressed Acetyl Xylan Esterase1 Isolated from the Anaerobic Rumen Fungus Neocallimastix frontalis PMA02

Characterization of Heterologously Expressed Acetyl Xylan Esterase1 Isolated from the Anaerobic Rumen Fungus <i>Neocallimastix frontalis</i> PMA02

Animal Bioscience, June 2016

27383808

Mi Kwon, Jaeyong Song, Hong-Seog Park, Hyunjin Park, Jongsoo Chang

Acetyl xylan esterase (AXE), which hydrolyzes the ester linkages of the naturally acetylated xylan and thus know to have important role for hemicellulose degradation, was isolated from the anaerobic rumen fungus Neocallimastix frontatlis PMA02, heterologously expressed in E.coli and characterized. The full-length cDNA encoding N. frontalis AXE1 was 1,494 bp, of which 978 bp constituted an open reading frame. The estimated molecular weight of NfAXE1 was 36.5 kDa with 326 amino acid residues, and the calculated isoelectric point was 4.54. The secondary protein structure was predicted to be consisted of nine α-helixes and 12 β-strands. The enzyme expressed in Escherichia coli had the highest activity at 40 ℃ and pH 8. The purified recombinant NfAXE1 had a specific activity of 100.1 U/mg when p-nitrophenyl acetate (p-NA) was used as a substrate at 40 ℃, optimum temperature. The amount of liberated acetic acids were the highest and the lowest when p-NA and acetylated birchwood xylan were used as substrates, respectively. The amount of xylose released from acetylated birchwod xylan was increased by 1.4 fold when NfAXE1 was mixed with xylanase in a reaction cocktail, implying a synergistic effect of NfAXE1 with xylanase on hemicellulose degradation.