title: The wood rot ascomycete Xylaria polymorpha produces a novel GH78 glycoside hydrolase that exhibits α-L-rhamnosidase and feruloyl esterase activities and releases hydroxycinnamic acids from lignocelluloses.
abstract: Soft rot (type II) fungi belonging to the family Xylariaceae are known to substantially degrade hardwood by means of their poorly understood lignocellulolytic system, which comprises various hydrolases, including feruloyl esterases and laccase. In the present study, several members of the Xylariaceae were found to exhibit high feruloyl esterase activity during growth on lignocellulosic materials such as wheat straw (up to 1,675 mU g(-1)) or beech wood (up to 80 mU g(-1)). Following the ester-cleaving activity toward methyl ferulate, a hydrolase of Xylaria polymorpha was produced in solid-state culture on wheat straw and purified by different steps of anion-exchange and size-exclusion chromatography to apparent homogeneity (specific activity, 2.2 U mg(-1)). The peptide sequence of the purified protein deduced from the gene sequence and verified by de novo peptide sequencing shows high similarity to putative α-L-rhamnosidase sequences belonging to the glycoside hydrolase family 78 (GH78; classified under EC 3.2.1.40). The purified enzyme (98 kDa by SDS-PAGE, 103 kDa by size-exclusion chromatography; pI 3.7) converted diverse glycosides (e.g., α-L-rhamnopyranoside and α-L-arabinofuranoside) but also natural and synthetic esters (e.g., chlorogenic acid, hydroxycinnamic acid glycoside esters, veratric acid esters, or p-nitrophenyl acetate) and released free hydroxycinnamic acids (ferulic and coumaric acid) from arabinoxylan and milled wheat straw. These catalytic properties strongly suggest that X. polymorpha GH78 is a multifunctional enzyme. It is the first fungal enzyme that combines glycosyl hydrolase with esterase activities and may help this soft rot fungus to degrade lignocelluloses.
authors.affiliation: Unit of Environmental Biotechnology, International Graduate School of Zittau, Zittau, Germany.
authors.forename: Do Huu
authors.initials: do H
authors.lastname: Nghi
authors.forename: Britta
authors.initials: B
authors.lastname: Bittner
authors.forename: Harald
authors.initials: H
authors.lastname: Kellner
authors.forename: Nico
authors.initials: N
authors.lastname: Jehmlich
authors.forename: René
authors.initials: R
authors.lastname: Ullrich
authors.forename: Marek J
authors.initials: MJ
authors.lastname: Pecyna
authors.forename: Paula
authors.initials: P
authors.lastname: Nousiainen
authors.forename: Jussi
authors.initials: J
authors.lastname: Sipilä
authors.forename: Le Mai
authors.initials: le M
authors.lastname: Huong
authors.forename: Martin
authors.initials: M
authors.lastname: Hofrichter
authors.forename: Christiane
authors.initials: C
authors.lastname: Liers
mesh_terms: D002265:Carboxylic Ester Hydrolases / Q000235:genetics / Q000378:metabolism*; D003373:Coumaric Acids / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008031:Lignin / Q000378:metabolism*; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D013379:Substrate Specificity; D014934:Wood / Q000378:metabolism / Q000382:microbiology*; D013098:Xylariales / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
chemical_list: D003373:Coumaric Acids; C036909:lignocellulose; D008031:Lignin; D002265:Carboxylic Ester Hydrolases; C070196:feruloyl esterase; D006026:Glycoside Hydrolases; C022525:alpha-L-rhamnosidase