lecture 6 + extra material enzymes

Question 1

Describe how to determine whether two proteins are related by convergent or divergent
evolution.

Answer 1

When two proteins are related by convergent evolution, it means that unrelated proteins have evolved a similar function. An example of this is the bacterial serine protease subtulisin, which shows no sequence similarity to chymotryp-sin and no overall structural similarity, although it has the same Asp-His-Ser
catalytic triad and an oxyanion hole in its active site.
Divergent evolution is when two proteins evolved from a common ancestor and retained their overall structure and catalytic mechanism (even though they may have gotten a different amino acid sequence over time)

Question 2

What are the other ways in which enzyme activity can be regulated? (Besides by inhibitors binding to them)

Answer 2

1. A change in the amount of the enzyme. (So, a change in its synthesis and degradation)
2. A change in the enzyme’s location, bringing it to or from its substrate.
3. An ionic signal (Ca2+ or altering pH) can change an enzyme’s conformation
4. Covalent modification of an enzyme. (Most common is the addition of a phosphoryl group)