Characterization of Acetylxylan Esterase from White-Rot Fungus .

The carbohydrate esterase family 1 (CE1) in CAZy contains acetylxylan esterases (AXEs) and feruloyl esterases (FAEs). Here we cloned a gene coding for an AXE belonging to CE1 from (AXE1). AXE1 was heterologously expressed in , and the recombinant enzyme was purified and characterized. AXE1 hydrolyzed -nitrophenyl acetate, α-naphthyl acetate and 4-methylumbelliferyl acetate, however, it did not show any activity on ethyl ferulate and methyl -coumarate. We also examined the activity on partially acetylated and feruloylated xylan extracted from corncob by hydrothermal reaction. Similarly, ferulic and -coumaric acids were not liberated, and acetic acid was only detected in the reaction mixture. The results indicated that AXE1 is an acetylxylan esterase actually reacted to acetyl xylan. However, since AXE1 was unable to completely release acetic acid esterifying xylopyranosyl residues, it is assumed that acetyl groups exhibiting resistance to deacetylation by AXE1 are present in corn cob xylan.