Zoom in on microorganisms

Genetic engineering to the rescue of diabetics

How do they actually make insulin?

How do they actually make insulin?

© Armand-Frappier Museum

The insulin-production process is the same regardless of whether yeast or bacteria are used. First, the gene (a segment of DNA strand) which controls the production of human insulin is inserted into the microorganism. The microorganism, believing the hormone necessary for its survival, produces insulin which is subsequently collected, purified and marketed.

A first!
Insulin production was the first industrial application of this technique in which a bacterium possessing a human gene was used to produce a molecule for human use.

The discovery of insulin: Almost as Canadian as maple syrup!
Did you know that insulin was first isolated, from dogs, in 1922 by four Canadians at the University of Toronto? The insulin was given to a young 14-year-old diabetic named Leonard Thompson, and saved his life! The following year, two of the researchers, Banting and Macleod, received the Nobel Prize. This aggravated tensions which had developed in the group by then, despite the fact that the Nobel laureates shared the prize with the two other researchers, Best and Collip.

Structure of insulin
Insulin is composed of two subunits (two chains named A and B) connected to each other by chemical bonds known as disulphide bridges. Note that because the chains are formed of amino acids, insulin is in fact a protein.

What about proinsulin?
The body also produces proinsulin, a precursor of insulin. Because insulin is made up of two chains, the cells must ensure that the chains are properly oriented to each other. The most practical way of making sure that both chains maintain the proper physical relation to each other is to connect them. This connection phase, proinsulin, is made up of two chains (A and B) connected to a third chain known as Peptide C. When proinsulin folds up, bonds form between chains A and B, and Peptide C, which connected them, is removed, yielding active insulin.

How do companies that produce insulin do it?
The first attempts to produce insulin with microorganisms attempted to produce chains A and B separately and connect them chemically. Studies of proinsulin revealed that the body has a much better way of doing things. This method was borrowed, and applied in the microorganisms that produce insulin. Today, yeasts and bacteria produce proinsulin, and Peptide C (which connects chains A and B) is eliminated, just as in humans. That's all there is to it!