Question

Q.3. What kind of post-translational modifications are taking place on collagen? (there are many. So please check the literature carefully). Why are they important for its structure? In terms of post translational processing of collagen, explain why chicken soup that is liquid when cooked fresh, becomes a gel like material upon refrigeration overnight.

Answer 1

post-translational modifications on collagen

1) hydroxylation of selected proline and lysine amino acids in the newly synthesized procollagen protein. Specific enzymes called hydroxylases are responsible for these important reactions needed to form hydroxyproline and hydroxylysine.

2) In the extracellular spaces, another post-translational modification takes place as the triple helical collagen molecules line up and begin to form fibrils and then fibers. . This step is called crosslink formation and is promoted by another specialized enzyme called lysyl oxidase. This reaction places stable crosslinks within and between the molecules.

This is the critical step that gives the collagen fibers such tremendous strength. On a per weight basis, the strength of collagen approaches the tensile strength of steel.

When you simmer a fresh chicken you extract the collagen from the bones. This collagen in the bones is what is causing your soup to gel. Because of the post-translational modifications of collagen which form fibrils.