1. Proteinaceous Nature: 

All enzymes are basically made up of protein. 

2. Three-Dimensional conformation: 

a. All enzymes have specific 3-dimensional conformation. 

b. They have one or more active sites to which substrate (reactant) combines. 

c. The points of active site where the substrate joins with the enzyme is called substrate binding site. 

3. Catalytic property: 

a. Enzymes are like inorganic catalysts and influence the speed of biochemical reactions but themselves remain unchanged. 

b. After completion of the reaction and release of the product they remain active to catalyze again. 

c. A small quantity of enzymes can catalyze the transformation of a very large quantity of the substrate into an end product. 

d. For example, sucrase can hydrolyze 100000 times of sucrose as compared with its own weight. 

4. Specificity of action: 

a. The ability of an enzyme to catalyze one specific reaction and essentially no other is perhaps its most significant property. Each enzyme acts upon a specific substrate or a specific group of substrates. 

b. Enzymes are very sensitive to temperature and pH. 

c. Each enzyme exhibits its highest activity at a specific pH i.e. optimum pH. 

d. Any increase or decrease in pH causes decline in enzyme activity e.g. enzyme pepsin (secreted in stomach)shows highest activity at an optimum pH of 2 (acidic) 

5. Temperature: 

a. Enzymes are destroyed at higher temperature of 60-70°C or below, they are not destroyed but become inactive. 

b. This inactive state is temporary and the enzyme can become active at suitable temperature. 

c. Most of the enzymes work at an optimum temperature between 20°C and 35°C. 

There are two types of models: 

1. Lock and Key model: 

a. Lock and Key model was first postulated in 1894 by Emil Fischer.

b. This model explains the specific action of an enzyme with a single substrate. 

c. In this model, lock is the enzyme and key is the substrate. 

d. The correctly sized key (substrate) fits into the key hole (active site) of the lock (enzyme).