Yield improvement of heterologous peptides expressed in yps1-disrupted Saccharomyces cerevisiae strains

Heterologous protein expression levels in Saccharomyces cerevisiae fermenta tions are highly dependent on the susceptibility to endogenous yeast protea ses. Small peptides, such as glucagon and glucagon-like-peptides (GLP-1 and GLP-2), featuring an open structure are particularly accessible for proteo lytic degradation during fermentation. Therefore, homogeneous products cann ot be obtained. The most sensitive residues are found at basic amino acid r esidues in the peptide sequence. These heterologous peptides are degraded m ainly by the YPS1-encoded aspartic protease, yapsin1, when produced in the yeast. In this article, distinct degradation products were analyzed by HPLC and mass spectrometry, and high yield of the heterologous peptide producti on has been achieved by the disruption of the YPS1 gene (previously called YAP3). By this technique, high yield continuous fermentation of glucagon in S. cerevisiae is now possible. (C) 2000 Elsevier Science Inc. All rights r eserved.