•Human -Genetically
engineered using either yeast (pyr) or e.coli (prb)
•Animal
–Beef-Increased
incidence of allergic problems
–Pork-Less antigenic than beef (Kurtz et al. 1980)
•-Available as purified insulin
–
Human insulin is
the most used insulin. It is genetically engineered and is indistinguishable
from the naturally occurring human insulin.
Originally beef
insulin was used but was found to cause problems in some patients. This is
due to the body recognising the injected protein as foreign. This is less
marked with porcine insulin but obviously it makes sense to use an identical
insulin to that which the body would normally produce.