Highlights Enzymes I

1. We aim to use cells and organisms to produced products in biotechnology, but to understand that, we must understand the molecular basis by which cells make things. This requires knowledge of enzymes.

2. Enzymes are proteins that catalyze reactions.

3. Chemical catalysts speed reactions without themselves being altered. Enzymes are millions of times more effective than chemical catalysts.

4. One reason for the difference in efficiency of enzymes compared to chemical catalysts is that enzymes are flexible and use their flexibility in their catalysis.

5. Molecules that enzymes bind to and catalyze reactions on are called substrates. The location in an enzyme where a substrate is bound is called the active site. This is the place in the enzyme where the reaction occurs.

6. Proteins contain 20 amino acids and the sequence with which these are linked together. This sequence governs all the properties of a protein. (Remember that enzymes are proteins).

7. One of the most important characteristics of a protein is its shape. If a protein loses its shape, it loses its ability to function.

8. Some proteins hold their shape very well despite being heated or in solutions of detergent or acid. Others don't hold their shape very well and lose function under these conditions.

9. The differences in the ability of proteins to hold their shape is determined by the amount of stabilizing structures proteins have to help hold the shape. These include disulfide bonds (sulfur-sulfur covalent bonds) and hydrogen bonds (between OH and H groups). Disulfide bonds are very strong. Hydrogen bonds are not so strong.

10. The 20 amino acids found in proteins have different chemical properties. Some dissolve readily in water (hydrophilic) and some do not (hydrophilic).

11. Most enzymes are dissolved in water, but have both hydrophilic and hydrophobic amino acids. They are able to dissolve in water by "hiding" the hydrophobic amino acids on their insides when they fold up so as to avoid contact with water. The hydrophilic amino acids, by contrast are located on the outside of the protein so they help the protein to dissolve in water.

12. Enzymes act by lowering the "activation energy" needed to get a reaction started. Uncatalyzed reactions have a higher activation energy than uncatalyzed reactions. Enzymes do not change the beginning or ending energies of molecules, only the activation energy needed to start the reaction.

13. Important enzymes industrially include enzymes that break down proteins (pepsin, trypsin, chymotrypsin), enzymes that break down fats (lipases), and enzymes that break dow