Yeasts are attractive hosts for production of mammalian proteins requiring posttranslational processing, because yeasts offer advantages of both eukaryotic expression mechanisms and bacteria-like growth and handling. Thus for the past 22 years yeasts have been used to overcome the shortcomings of bacterial expression systems. As in Escherichia coli yeasts can provide intracellular as well as secreted expression. By applying short signaling sequences, the expressed proteins can be directed to extracellular secretion or to distinct compartments of the cell (1). Because Saccharomyces cerevisiae tends to hyper-glycosylate secreted proteins, this strain is primarily used for intracellular production. Other yeast strains (i.e., Pichia pastoris, Hansenula polymorpha, Schizosaccharomyces pompe, Klyveromyces lactis, or Yarrowia lipolytica) are more suited for secretion (2).