title: The effect of nitrogen source on yield and glycosylation of a human cystatin C mutant expressed in Pichia pastoris.
abstract: Human cystatin C is a cysteine proteinase inhibitor with potential applications as an anti-viral agent, cancer tumor growth inhibitor, and in prevention of proteolysis during food processing. A glycosylated cystatin C mutant with increased temperature stability was developed for the latter application [Nakamura et al. (1998) FEBS Lett 427:252-254]. A recombinant variant of cystatin C [Nakamura et al. (2000) International patent no. PLTCA99/00717] with two potential sites for N-linked glycosylation was expressed in Pichia pastoris Mut(s). Little of the cystatin C produced was in the glycosylated form under fermentation conditions of pH 6, temperature 28 degrees C, methanol only feed, and ammonium hydroxide as a nitrogen source. Thus, the effect of addition of complex nitrogen sources, peptone and amino acid supplements, on the yield and glycosylation of this mutant cystatin C were investigated. A full factorial design experiment using 2-l fermenters was performed with three factors: ammonium hydroxide, peptone, and an amino acid mix, at two levels, absent or present. Peptone addition was found to have a positive, and the most significant, effect on cell specific cystatin C yield. A maximum mutant cystatin C yield of 0.82 mumol (g-dry cell weight)(-1) min(-1) was obtained when all three nitrogen sources were used together. However, under these conditions only 16% of protein was in the glycosylated form since ammonia was found to have a significant negative effect on glycosylation extent. The maximum extent of glycosylation was 30% when peptone and amino acid mix were the only nitrogen sources added.
authors.affiliation: Chemical and Biological Engineering, University of British Columbia, 2357 Main Mall, Vancouver, BC, V6T 1Z4, Canada.
authors.forename: Jason
authors.initials: J
authors.lastname: Pritchett
authors.forename: Susan A
authors.initials: SA
authors.lastname: Baldwin
mesh_terms: D003470:Culture Media; D055316:Cystatin C; D015891:Cystatins / Q000235:genetics / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000235:genetics / Q000378:metabolism; D005285:Fermentation; D006031:Glycosylation; D006801:Humans; D007218:Industrial Microbiology / Q000379:methods*; D009154:Mutation; D009584:Nitrogen / Q000378:metabolism*; D010843:Pichia / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
chemical_list: C525030:CST3 protein, human; D003470:Culture Media; D055316:Cystatin C; D015891:Cystatins; D015853:Cysteine Proteinase Inhibitors; D009584:Nitrogen