부산대학교 도서관

The Mucorrennin gene encoding a prepro-form of the fungal aspartic proteinase from Mucor pusilluswas expressed under the control of the yeast GAL7promoter in Saccharomyces cerevisiae. An inactive zymogen of the enzyme with the 44-amino-acid pro-sequence was identified in the medium during the initial stage of cultivation. Processing of the purified zymogen to the mature enzyme proceeded autocatalytically under the acidic conditions. The rate of processing was accelerated by an increase in the concentration of the zymogen or addition of the mature enzyme. The in vitroprocessing was inhibited by inhibitors for the aspartic proteinases. The zymogen with no proteinase activity due to a mutation at the active site residue, Asp, was still processed at a relatively slower rate in a wild-type strain of yeast, but no processing occurred in the pep4-3mutant strain of S. cerevisiaedeficient in yeast proteinase A. Thus, Mucorrennin is excreted in a form of zymogen, which is then processed in the yeast secretion pathway mainly by the autocatalytic proteolysis but, alternatively, by a proteinase of yeast.