Expression of a catalytic domain of a Neocallimastix frontalis endoxylanase gene (xyn3) in Kluyveromyces lactis and Penicillium roqueforti

A cDNA fragment encoding the A catalytic domain of the Neocallimastix front alis endoxylanase XYN3 was amplified and cloned by the polymerase chain rea ction technique. The xyn3A DNA fragment was inserted between the Saccharomy ces cerevisiae phosphoglycerate kinase gene promoter and terminator sequenc es on a multicopy episomal plasmid for Kluyveromyces lactis. The XYN3A doma in was successfully expressed in K. lactis and functional endoxylanase was secreted by the yeast cells with the K. lactis killer toxin secretion signa l. The XYN3A domain was also expressed in a strain of Penicillium roquefort i as a fusion protein (ShBLE::XYN3A) of the phleomycin-resistance gene prod uct and the endoxylanase. Active endoxylanase was efficiently secreted from the fungal cells with the Trichoderma viride cellobiohydrolase (CBH1) secr etion signal and processed by a related KEX2 endoprotease of the secretion pathway. Several differently glycosylated forms of the recombinant enzymes were secreted by the yeast and the filamentous fungus.