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Unusual Microbial Xylanases from Insect Guts

2004; American Society for Microbiology; Volume: 70; Issue: 6 Linguagem: Inglês

10.1128/aem.70.6.3609-3617.2004

1098-5336

Yali Brennan, Walter Callen, Leif Christoffersen, Paul Dupree, Florence Goubet, Shaun Healey, M A Yanez Hernandez, Martin Keller, Ke Li, Nisha Palackal, Ana Sittenfeld, Giselle Tamayo‐Castillo, Steve Wells, Geoffrey P. Hazlewood, Eric J. Mathur, Jay M. Short, Dan E. Robertson, Brian A. Steer,

Insect and Arachnid Ecology and Behavior

ABSTRACT Recombinant DNA technologies enable the direct isolation and expression of novel genes from biotopes containing complex consortia of uncultured microorganisms. In this study, genomic libraries were constructed from microbial DNA isolated from insect intestinal tracts from the orders Isoptera (termites) and Lepidoptera (moths). Using a targeted functional assay, these environmental DNA libraries were screened for genes that encode proteins with xylanase activity. Several novel xylanase enzymes with unusual primary sequences and novel domains of unknown function were discovered. Phylogenetic analysis demonstrated remarkable distance between the sequences of these enzymes and other known xylanases. Biochemical analysis confirmed that these enzymes are true xylanases, which catalyze the hydrolysis of a variety of substituted β-1,4-linked xylose oligomeric and polymeric substrates and produce unique hydrolysis products. From detailed polyacrylamide carbohydrate electrophoresis analysis of substrate cleavage patterns, the xylan polymer binding sites of these enzymes are proposed.