Products derived from genetically engineered microorganisms
Recombinant DNA technology can be used to genetically modify microorganisms so that they produce commercially important proteins such as human insulin. This is done by incorporating the gene for the desired protein into an appropriate cloning vector, and inserting it into a host cell such as E. coli or Saccharomyces cerevisiae.
The initial application of this technology was in the micro-bial production of medically important proteins such as insulin and epidermal growth factor (Table 17.6), however other proteins may also be produced by these means. These include enzymes used in diagnostic and analytical applications, where a higher purity of preparation is required than, for example, the enzymes used in detergents. These are often derived originally from other microorganisms; for example the thermostable DNA polymerase from Thermus aquaticus used in PCR is now commonly made by recombinant E. coli cells that have been transformed with the T. aquaticus gene. Many of the more recent recombinant human proteins to be developed for therapeutic use have been too complex for expression in a microbial system (e.g. Factor VIII), so it has been necessary to employ cultured mammalian cells.