Secretion of a Cryptococcus albidus xylanase in Saccharomyces cerevisiae.

The xylanase(XLN)-encoding gene(XLN) of Cryptococcus albidus and its cDNA were each inserted into the vector, pVT100, for expression in Saccharomyces cerevisiae. Expression was under the control of either their own promoter or the gene encoding alcohol dehydrogenase (ADH1) promoter. Yeast transformed with plasmids containing the cDNA of the structural XLN gene and the XLN promoter produced active extracellular XLN when grown with galactose as carbon source. However, with glucose as carbon source, XLN was repressed. Using the ADH1 promoter, which is stimulated by glucose, XLN was secreted into the culture medium. In both cases, the secreted 48-kDa enzyme corresponded to the native XLN produced by C. albidus. With the plasmid bearing the genomic XLN gene, there was transcription, but the seven introns interrupting XLN were not spliced out by S. cerevisiae and no enzyme was produced.