Enzymes are complex protein molecules with three dimensional structures. They catalyse the chemical reaction in living organism. They are often present in colloidal state and extremely specific in catalytic action. This process is called enzyme catalysis.
Special characteristics of enzyme catalysis:
1. Effective and efficient conversion is the special characteristic of enzyme catalysed reactions. An enzyme may transform a million molecules of reactant in a minute.
For e.g., 2H2O2 → 2H2O + O2
For this reaction, activation energy is 1 8k.cal/mole without a catalyst. With colloidal platinum as a catalyst, the activation energy is 11.7 k.cal/mole. But with the enzyme catalyst. the activation energy of this reaction is less than 2 k.cal / mole.
2. Enzyme catalysis is highly specific in nature.
H2N – CO – NH2 + H2O → 2NH3 + H2O
The enzyme urcase which catalyses the reaction of urea does not catalyse the hydrolysis of methyl urea (NH2 – CO – NHCH3)
3. Enzyme catalysed reaction has maximum rate at optimum temperature. At first rate of the reaction increases with increase of temperature, but above a particular temperature, the activity of enzyme is destroyed. The rate may even drop to zero. The temperature at which enzyrnic activity is high (or) maximum is called as optimum temperature. e.g., enzyme involved in human body have an optimum temperature 37°C / 98°F.
4. The rate of enzyme catalysed reactions varies with the pH of the system. The rate is maximum at a pH called optimum pH.
5. Enzymes can be inhibited i.e., poisoned. Activity of an enzyme is decreased and destroyed by a poison. The physiological action of drugs is related to their inhibiting action. e.g.. sulpha drugs, penicillin inhibits the action of bacteria and used for curing diseases like pneumonia, dysentery, cholera.
6. Catalytic activity of enzymes is increased by coenzymes or activators. A small non protein (vitamin) called a coenzyme promotes the catalytic activity of enzyme.
