Scientists from GlycoFi, Inc., a wholly owned subsidiary of Merck & Co., Inc., and their collaborators at Dartmouth-Hitchcock Medical Center published their report detailing the genetic engineering of the yeast Pichia pastoris to secrete human glycoproteins with fully complex, terminally sialyated N-glycans today in the September 8, 2006 issue of the journal Science. To demonstrate the utility of the engineered yeast strains, recombinant erythropoietin (Epo), a protein that stimulates the production of red blood cells, was expressed, purified and its activity demonstrated in vivo.
"Re-engineering the yeast glycosylation system to fully replicate the full repertoire of human glycosylation reactions has been a challenging six year effort that many doubted could be accomplished," said Tillman Gerngross, Ph.D., chief scientific officer of GlycoFi and professor of Bioengineering at Dartmouth College.
"This achievement required both the elimination of yeast-specific glycosylation reactions and the introduction of 14 heterologous genes, making this one of the most complex cellular engineering endeavors reported to date", said Stephen Hamilton, Ph.D., the lead author of the study and a senior scientist at GlycoFi.
Yeast offers numerous advantages as a recombinant protein expression system when compared to mammalian cell culture. These include the capability