Practical examples of the rational design of a large drug molecule and post-translational modification

Question 1

Insulin production

Answer 1

Purified animal sourced insulin was the only type of insulin available to diabetics until genetic advances occurred later with medical research
The first genetically engineered, synthetic human insulin was produced using the bacterium E coli in 1978- protein does not require glycosylation to be biologically active
Currently human insulin made from bacteria are almost twice as expensive as porcine insulin

Question 2

Insulin production in humans

Answer 2

Cleavage of signal peptide by signal peptidase
Disulfide bond formation
Cleavage by trypsin-like enzymes releases the C peptide
The C chain is packaged in the secretory vesicle and is secreted along with active insulin
Further trimming by a carboxypeptidase B-like enzyme removes two basic residues from each of the new ends

Question 3

Interferons

Answer 3

Glycoproteins
Hinder the replication of viruses
Affect the immune response
Three types of interferon: alpha, beta and gamma
Relatively quickly broken down, need for repeated injection

Question 4

Addition of sugar groups to antibodies

Answer 4

All antibodies are glycosylated at conserved positions in their constant regions
Affect antibody activity by complement binding and attachment to immune cells
Antibody glycosylation can be influenced by the cell culture conditions

Question 5

Mouse produced MAB antibody

Answer 5

Recognised as foreign by human immune system
Have murine glycoslyation patterns
Do not bind efficiently to immune effector cells via FC receptors