Enzymes Classification and Activity Factors

Study Notes

Enzymes are grouped into six major classes
Oxidoreductases: These enzymes catalyze oxidation-reduction reactions, examples include dehydrogenases and oxidases.
Transferases: Transfer functional groups (e.g., amino or phosphate groups) between donors and acceptors, examples include aminotransferases and kinases.
Hydrolases: Hydrolases use water to catalyze the hydrolysis of substrates. Examples include proteases and phosphatases.
Lyases: These enzymes add or remove the elements of water, ammonia, or carbon dioxide from or to double bonds. Examples include decarboxylases and synthases.
Isomerases: These enzymes catalyze changes within one molecule. Mutases are an example.
Ligases: These enzymes join two molecules together at the expense of ATP. Examples include synthetases and carboxylases.

Substrate concentration: Increasing substrate concentration increases reaction velocity up to a point (Vmax). At Vmax, further substrate increases have no effect on velocity.
Enzyme concentration: Increased enzyme concentration increases reaction velocity.
pH: Enzyme activity is optimal at a specific pH. Deviations above or below the optimal pH decrease the reaction rate. Each enzyme has its own optimal pH.
Temperature: Increasing temperature increases reaction velocity up to an optimum, after which, velocity decreases due to enzyme denaturation. Most enzymes denature at 55-60°C.