Recombinant Human Proteins (Cambridge International A-Level Biology)

Spec point — 19.2.1 · explain the advantages of using recombinant human proteins to treat disease, using the examples insulin, factor VIII and adenosine deaminase

Recombinant human proteins

• DNA that has been altered by introducing nucleotides from another source is called recombinant DNA(rDNA)

  • DNA from one organism has been recombined with DNA from another source

• If the organism contains nucleotides from a different species it is called a **transgenic **organism

• Any organism that has received genetic material from another source is a genetically modified organism (GMO)

• Recombinant DNA has been used to produce** recombinant proteins** (RP), recombinant human proteins can be identical to the natural human protein, or deliberately modified (e.g. faster-acting insulin)

• Recombinant proteins are generated using microorganisms such as bacteria, yeast, or animal cells in culture

  • They are used for research purposes and for treatments (e.g., diabetes, cancer, infectious diseases, haemophilia)

• Most recombinant human proteins are produced using eukaryotic cells (e.g. yeast, or animal cells in culture) rather than using prokaryotic cells because eukaryotic cells will carry out the post-translational modification

• Due to the presence of Golgi apparatus (and/or enzymes) that is required to produce a suitable human protein

• The advantages of genetic engineering organisms to produce recombinant human proteins are:

  • More cost-effective to produce large volumes (i.e. there is unlimited availability)
  • Simpler (with regards to using prokaryotic cells)
  • Faster to produce many proteins
  • Reliable supply available
  • The proteins are engineered to be identical to human proteins or have modifications that are beneficial
  • It can solve the issue for people who have moral, ethical or religious concerns against using cow or pork-produced proteins

Insulin

• In 1982, insulin was the first recombinant human protein to be approved for use in diabetes treatment

• Bacteria plasmids are modified to include the human insulin gene

  • Restriction endonucleases are used to cut open plasmids and DNA ligase is used to splice the plasmid and human DNA together

• These recombinant plasmids are then inserted into the bacterium Escherichia coli by transformation (bath of calcium ions and then heat or electric shock)

• Once the transgenic bacteria are identified (by the markers), they are isolated, purified and placed into fermenters that provide optimal conditions

• The transgenic bacteria multiply by binary fission and express the human protein - insulin, which is eventually extracted and purified

• The advantages for scientists to use recombinant insulin are:

  • It is identical to human insulin, unless modified to have different properties (eg. act faster, which is useful for taking immediately after a meal or to act more slowly)
  • There is a reliable supply available to meet demand (no need to depend on the availability of meat stock)
  • Fewer ethical, moral or religious concerns (proteins are not extracted from cows or pigs)
  • Fewer rejection problems, side effects or allergic reactions
  • Cheaper to produce in large volumes
  • Is useful for people who have animal insulin tolerance

Factor VIII

• Factor VIII is a blood-clotting protein that haemophiliacs cannot produce

• Kidney and ovary hamster cells have been genetically modified to produce Factor VIII

• Once modified, these recombinant cells are placed into a fermenter and cultured

• Due to the optimal conditions in the fermenter, the hamster cells constantly express Factor VIII which can then be extracted, purified and used as an injectable treatment for haemophilia

• The advantages for scientists to use recombinant Factor VIII are:

  • Fewer ethical, moral or religious concerns (proteins are not extracted from human blood)
  • Less risk of transmitting infection (eg. HIV) or disease
  • Greater production rate

Adenosine deaminase

• Adenosine deaminase (ADA) is an enzyme used to treat the inherited condition called Adenosine Deaminase Deficiency

• ADA Deficiency is a common cause of Severe Combined Immunodeficiency (SCID)

• This is because the immune system is damaged

• The larva of the cabbage looper moth (Trichoplusia ni) has been genetically modified (using a virus vector) to produce the enzyme adenosine deaminase so that it can be used as a treatment whilst the patients wait for gene therapy or when gene therapy is not possible

• The advantages for scientists to use recombinant adenosine deaminase are:

  • Fewer ethical, moral or religious concerns (proteins are not extracted from cows)
  • Less risk of transmitting infection or disease (from cows)
  • More reliable production of the enzyme
  • Faster to produce many proteins

Exam Hint Learn how recombinant human insulin is produced and the advantages of recombinant human insulin being used to treat diabetes.