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Title: Identification of Genes Encoding Microbial Glucuronoyl Esterases

Author
item Li, Xin Liang
item SPANIKOVA, SILVIA - SLOVAK ACADEMY OF SCIENCE
item DE VRIES, RONALD - UTRECHT UNIVERSITY
item BIELY, PETER - SLOVAK ACADEMY OF SCIENCE

Submitted to: The Federation of European Biochemical Societies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/16/2007
Publication Date: 12/1/2007
Citation: Li, X., Spanikova, S., De Vries, R.P., Biely, P. 2007. Identification of Genes Encoding Microbial Glucuronoyl Esterases. The Federation of European Biochemical Societies. 581(21):4029-4035.

Interpretive Summary: Efficient conversion of lignocellulosic biomass to fermentable sugars has been recognized as the major bottleneck for the economical production of biofuels and feedstock chemicals from the almost infinite renewable resources. There are three major constitutes, cellulose, hemicellulose, and lignin, commonly found in lignocellulosic biomass. Covalent linkages between hemicellulose and lignin have been discovered for a long time but microbial enzymes responsible for their cleavages have not yet been described. Recently, our collaborator, Professor Peter Biely, discovered that a fungal esterase specifically hydrolyzes the methyl ester bond of 4-O-methyl-D-glucuronidic acid, a side group commonly found in hemicellulose. The work provided evidence that such enzymes might be responsible for breaking the ester linkages between hemicellulose and lignin. The paper we are describing here reports the genes encoding this group of esterases. All the genes described in here were found through genomic approaches, but their function was unknown.

Technical Abstract: One type of covalent linkages connecting lignin and hemicellulose in plant cell walls is the ester linkage between 4-0-methyl-D-glucuronic acid of glucuronoxylan and lignin alcohols. An enzyme that could hydrolyze such linkages, named glucuronoyl esterase, occurs in the cellulolytic system of the wood-rotting fungus Schizophyllum commune. Here we report partial amino acid sequences of the enzyme and the results of subsequent search for homologous genes in sequenced genomes. The homologous genes of unknown functions were found in genomes of several filamentous fungi and one bacterium. The gene corresponding to the cip2 gene of Hypocrea jecorina (Trichoderma reesei), known to be up-regulated under conditions of induction of cellulolytic and hemicellulolytic enzymes, was over-expressed in H. jecorina. The product of the cip2 gene was purified to homogeneity and shown to exhibit glucuronoyl esterase activity.