Enzymes as catalyst:-

Enzymes are the globular proteins which act as biological catalysts. Although enzymes are proteins, yet some enzymes are associated with a non protein component called the co-factor, for their activity. These co-factors are of two types:

1. Inorganic ions:- such as Zn⁺², Mg⁺², Fe⁺², K⁺, Na⁺ etc.
2. Organic molecules:- the organic Molecules are of two types:

1. Co-enzymes:- these are small organic molecules which are loosely held to the protein (enzymes) and can be easily separated. These are usually derived from Vitamins.
2. Prosthetic Group:- these are the organic molecules which are tightly held to the enzymes by covalent bond and can be separated only by careful hydrolysis. These are also derived from vitamins.

Every biological reaction requires a different kind of enzyme a typical cell contains about 3000 different type of enzymes each catalyzing different reaction. the enzyme increases the rate of reaction 10⁸ to 10²² times.

Properties of Enzymes:- Some important properties of enzymes are:

1. Specificity:- Each enzyme catalyses only one chemical reaction e.g. enzyme invertase hydrolysis only sucrose while enzyme maltase hydrolyses only maltose.

2.  Efficiency:- Enzymes are very efficient catalysts. They speed up the rate of reaction by 108 to 1020 times. For example a single meal which takes 5-6 hours for digestion in presence of enzymes would take 50 years to digest without enzymes.

3. Optimum Temperature and pH:- Enzyme catalysis reactions occur in aqueous solution at pH around 7.0 and at a physiological temperature of 37°C(310K).

4. Enzyme inhibitors:- the actions of enzymes are controlled by a number of mechanisms and are inhibited by certain organic molecules called inhibitors