Cloning and Characterization of the Gene Encoding Lipamide Dehydrogenase in Saccharomyces cerevisiae

been cloned and characterized. The LPDI gene is present as a single copy in the yeast genome and is transcribed to give a polyadenylated mRNA species of approximately 2.0 kb. The synthesis of lipoamide dehydrogenase in yeast is subject to carbon catabolite repression since both the level of the LPDl transcript and the accumulation of the lipoamide dehydrogenase subunit polypeptide were greatly reduced in wild-type cells grown on glucose compared to those grown on a variety of non-fermentable carbon sources. Strains defective in LPDl but transformed with the LPDl gene on a high copy number vector exhibited elevated levels of the LPDl transcript as well as increased lipoamide dehydrogenase activity when grown on glycerol. Immunoblotting experiments confirmed that such transformants over-expressed lipoamide dehydrogenase protein. Transcription from the LPDl sequence on plasmid pGP 1 still appeared to be subject to some catabolite repression despite the presence of multiple copies of the plasmid in the cell