A xylanase produced by the rumen anaerobic protozoan Polyplastron multivesiculatum shows close sequence similarity to family 11 xylanases from Gram-positive bacteria

We report for the first time the cloning and characterisation of a protozoa l enzyme involved in plant cell wall polysaccharide degradation. A cDNA lib rary was constructed from the ruminal protozoan Polyplastron multivesiculat um and a stable clone expressing xylanase activity was isolated. The encode d enzyme belongs to the glycoside hydrolase family 11, and phylogenetic ana lysis indicates a closer relationship with catalytic domains from Gram-posi tive bacteria than the other fibrolytic eukaryotes from the rumen, the anae robic fungi. (C) 1999 Published by Elsevier Science B.V. All rights reserve d.