CLONING AND CHARACTERIZATION OF THE PEPE GENE OF ASPERGILLUS-NIGER ENCODING A NEW ASPARTIC PROTEASE AND REGULATION OF PEPE AND PEPC

have cloned the pepE gene of Aspergillus niger, encoding an aspartic p rotease (PEPE): by screening a h genomic DNA library with a heterologo us probe, the Neurospora crassa gene coding for a vacuolar proteinase. Sequencing of pepE genomic and cDNA clones revealed that the gene con tains three introns, which are 91, 56 and 58-bp long. The deduced prot ein consists of 398 amino acids, has a putative signal sequence to all ow transport into the endoplasmic reticulum and probably undergoes a s econd proteolytic processing step at its N terminus to yield the matur e enzyme. The putative mature part of PEPE has extensive homology with other aspartic proteinases such as pepsins, cathepsins and, in partic ular, with proteinase A of Saccharomyces cerevisiae and pepsin 1 of Ca ndida albicans. Northern blot analyses revealed that cells contain an abundant pepE transcript whose amount does not change upon carbon or n itrogen limitation, the presence of proteins in the medium or changes in the pH of the medium. We also show that pepC, the A. niger homologu e of yeast protease B, is also expressed constitutively under these co nditions.