What are the types of enzymes?

Enzymes can be classified into 6 types based on the type of reaction in which they are used to catalyze. 

1. Oxidoreductases - Oxidoreductases catalyze oxidation reactions and reduction reactions, which involve the transfer of electrons from one form of molecule to another. They can be further classified into Oxidase (catalyzes oxidation reactions) and Reductase (catalyzes reduction reactions). An example is pyruvate dehydrogenase, which catalyzes the oxidation of pyruvate to acetyl coenzyme A.
2. Transferases - Transferases catalyze the transfer or exchange of functional groups among acceptors and donor molecules. Transaminase is a common example, which catalyzes the transfer of an amino group from one molecule to another.
3. Hydrolases - Hydrolases are hydrolytic enzymes. They catalyze the hydrolysis of substrates by adding water to cleave the bond. An example is pepsin, which hydrolyzes the peptide bonds in proteins. 
4. Lyases - Lyases catalyze the removal or addition of a group such as water, ammonia or carbon dioxide, to break to create double bonds. Aldolase is one such enzyme that plays a role in glycolysis. It catalyzes the breakdown of fructose-1, 6-bisphosphate to dihydroxyacetone phosphate and glyceraldehyde-3-phosphate. 
5. Isomerases - Isomerases catalyze the conversion or formation of an isomer of a compound, causing a change in its shape. Phosphoglucomutase is an example. It plays a role in catalyzing the conversion of glucose-1-phosphate to glucose-6-phosphate, in which a phosphate group is re-positioned in the same compound. 
6. Ligases - Ligases catalyze the association of two molecules into one molecular compound. Energy is released during the reaction. A common example is DNA ligase, which catalyzes the formation of a phosphodiester bond, allowing the two DNA fragments to join together.