O-Mannosylation of recombinant human insulin-like growth factor I (IGF-I) produced in Saccharomyces cerevisiae

A glycosylated form of recombinant human insulin-like growth factor I (IGF-I) expressed in Saccharomyces cerevisiaewas shown to contain mannose as the only carbohydrate constituent. All oligosaccharide chains of the glycoprotein could be released by mild alkaline treatment, and separated from the protein by gel-permeation chromatography on Bio-Gel P-2. The structures of these O-linked carbohydrate chains were determined by 500-MHz 1H-NMR spectroscopy, affording the disaccharide Manα1-2Man as the major component and the tetrasaccharide Manα1-3Manα1-2Manα1-2Man as a minor component. Reference oligosaccharides were prepared from mannoproteins released from the cell wall of S. cerevisiaeX2180 (α-wild type). In addition to previously reported structures, ranging from mannose to mannotetraose, the pentasaccharide Manα1-3Manα1-3Manα1-2Manα1-2Man was identified in the cell wall mannoprotein.