Engineering Protein Folding and Secretion Pathways to Enhance Productivity

Engineering Protein Folding and Secretion Pathways to Enhance Productivity 

pastoris is most favorably employed to produce secreted recombinant proteins. The major advantage is that the product is derived in a quite pure form after cell removal, so that recovery and purification are much easier than from cell lysates. Secondly, proteins that are naturally secreted in their native host often require the passage through the secretory pathway of the recombinant host for correct folding and processing. Most human proteins of potential therapeutic value are secretory proteins (antibodies, hormones, cytokines, enzymes), as well as many technical enzymes (e.g., cellulases, proteases, lipases, etc.), so that the secretory route is of high practical value. 

The ER is endowed with chaperones, protein disulfide isomerases and glycosylation enzymes, as well as their accessory proteins. Disulfide bond formation has frequently been observed to constitute a major bottleneck, and the overexpression of PDIl alone or in combination with its oxidase EROl was shown to enhance productivity of several proteins in P. pastoris [95, 119-123]. Also, the reinforcement of other ER-related processes was assessed with variable success [124, 125]. In particular, overproduction of Kar2 yielded unpredictable results, which can be explained by its cellular function as a signal molecule of the UPR 

It was demonstrated that glycoengineered proteins can be produced in the pilot scale [153] however, they have not reached the biopharmaceutical market to date. New strategies and perspectives oiP. pastoris glycoengineering have been reviewed recently [126]. 

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