The specificity of enzyms
Two general characteristics of enzyms:
- The structural part of enzyms is a protein. Att.: Every protein structure can be denaturated, in particular under influence of pH and temperature.
- Enzyms are (bio)catalysts and extremely specific and efficient; the holo-enzyme = apo-enzyme + co-enzym/prostetic group.
The activity of biocatalysts depends strongly of the molecular shape, in particular of the surface of that molecule.
For example: Imagine that certain molecules of the substrate (the reactant) want to react and make any product.
This will only be possible if those molecules do contact each other, and more: that they contact in the right way.
(Tow Train compartments also only connect in the right way).
If those molecules have to wait until - by accident - they collide in the right way, they can wait very long.
But look, there come the catalysts, the enzyms, to help out. They attract those molecules, fit them in their surface and thus these molecules are put toghether exactly in the right way, so they can react easy and fast.
When the molecules are toghether and connected, the enzyme will lose them and the new molecule is a fact.
Again: a substrate wants to react.It fits exactly in the surface of the enzym, close to the action centre. There arrived, the substrate can react easily (with help of the position a, b and c).
The reaction equation:
E + S 
ES E+P
S = substrate, P = product
The functioning of the enzyms has all to do with the surface of their molecules.
No matter what is changing that surface, the enzyme activity can be terribly disturbed.
Every enzyme has its own temperatur and pH where the activity is maximal: the optimal pH and temperature.
Question 30
In the following scheme you can see another type of enzyme catalysis.
Study the image and explain how the specificity of this enzyme is guaranteed.
Mistakes in the DNA (by mutation for example) can create confusion in the (human) body. Maybe wrong enzyms will be produces, so with a wrong threedimensional shape.
Such deficient enzyms make the normal biochemical reaction in the metabolism difficult or even impossible. Such a person suffers one or another illness.
Hemoglobine (Hb) can be considered a kind of enzyme with an activator. What activator has Hb?