The invention relates to enzymes having xylanase, mannanase and/or glucanaseactivity, e.g., catalyzing hydrolysis of internal .beta.-l,4-xylosidiclinkages or endo- .beta.-1,4- ghicanase linkages； and/or degrading a linearpolysaccharide beta-l ,4-xylan into xylose. Thus, the invention providesmethods and processes for breaking down hemicellulose, which is a majorcomponent of the cell wall of plants, including methods and processes forhydrolyzing hemicelluloses in any plant or wood or wood product, wood waste,paper pulp, paper product or paper waste or byproduct. In addition, methods ofdesigning new xylanases, mannanases and/or glucanases and methods of usethereof are also provided. The xylanases, mannanases and/or glucanases haveincreased activity and stability at increased pH and temperature.
