BioPharm International-02-09-2006

Over the last three decades, numerous protein expression systems have been developed with various quality requirements on large and small scales. Huge steps have been made in large-scale protein production in mammalian systems while the small-scale mammalian systems are expensive and inflexible. Thus, small-scale production is done in simpler expression systems, sometimes sacrificing the quality of the proteins. However, relief is on the way.

Yeast systems have been a staple for producing large amounts of proteins for industrial and biopharmaceutical use for many years. Yeast can be grown to very high cell mass densities in well-defined medium. Recombinant proteins in yeast can be over-expressed so the product is secreted from the cell and available for recovery in the fermentation solution. Proteins secreted by yeasts are heavily glycosylated at consensus glycosylation sites. Thus, expression of recombinant proteins in yeast systems historically has been confined to proteins where post-translations glycosylation patterns do not affect the function of proteins. Several yeast expression systems are used for recombinant protein expression, including Sacharomyces, Scizosacchromyces pombe, Pichia pastoris and Hansanuela polymorpha.

Managing codon pair interactions and simultaneously optimizing the entire set of parameters requires advanced computationally intensive design tools.

Rapid, efficient, and cost-effective protein expression and purification strategies are required for high throughput structural genomics and the production of therapeutic proteins. Fusion protein technology represents one strategy to achieve these goals. Fusion protein technology can facilitate purification, enhance protein expression and solubility, chaperone proper folding, reduce protein degradation, and in some cases, generate protein with a native N-terminus. No technology or reagent is a panacea, however, and establishing tools and optimal conditions for each protein remains an empirical exercise. With this in mind, protein fusions are a leading option to produce difficult-to-express proteins, especially in Escherichia coli.

The speed at which a recombinant protein product progresses into clinical trials is of vital importance for both small biotechnology companies as well as the biopharma groups of large pharmaceutical companies. For mammalian cell lines, two major impacts on the project timeline are the ability to quickly identify a product candidate and subsequently produce a high-expressing cell line for that product. The advent of various computer-based protein design methodologies and antibody discovery technologies for developing protein therapeutics has resulted in large numbers of protein or antibody variants that must be screened to identify the best clinical candidate.