What are the characteristics of enzymes ?

The characteristics of enzymes are :

1. Molecular weight : Enzymatic proteins are substances of high molecular weight. Peroxidase one of the smaller enzymes molecules has a molecular weight of 40,000 whereas catalase one of the largest has a molecular weight of 250,000 (Urease 483,000). Enzyme molecules are therefore larger than those of usual simple organic substances but are nevertheless small enough to dissolve completely in aqueous media to yield clear nonturbid solution

2. Amphoteric nature : Each molecule of enzyme possess numerous groups which yield Hydrogen ions in slightly alkaline solutions and groups which yield OH ions in slightly acidic solutions. Unlike many other substances therefore the enzymatic protein is amphoteric i. e., capable of ionizing either as an acid or as a base depending upon the acidity of the external solution.

3. Colloidal nature : They are colloid in nature due to which they present a large surface area for reactions to take place.

4. Specificity of enzymes : Enzymes are highly specific in nature i. e., a particular enzyme can catalyze only a particular type of reaction e.g., the enzyme malic dehydrogenase removes hydrogen atom from malic acid and not from other ketoacids. The enzymes possess active sites which are highly specific centres composed of varying number and sequence of amino acids. The active site possess a particular binding site which complexes only with specific substrate. Thus a suitable substrate fulfills the requirements of active site and closely fixes with it.

5. Heat sensitivity : Enzymes are inactivated or destroyed at temperatures considerably below the boiling point of water. At 50°C most enzymes in a liquid medium are inactivated. Slow inactivation takes place even at low temperatures. Some enzymes can endure temperatures of 100°C for short periods. But dried enzyme extracts can endure temperature of 100°C to 120°C or even higher. Thus enzymes are thermolabile.

6. Catalytic properties : Enzymes are active in extremely small amounts e.g., one molecule of invertase can effectively hydrolyze 1,000,000 times its own weight of sucrose. One molecule of catalase is able to catalyze conversion of 5,000,000 molecules of hydrogen peroxide. The enzyme is unchanged after the reaction.

7. Reversibility of reaction : Like a true catalyst enzymes have been found to accelerate the chemical reaction in either direction i.e., onwards and backward depending upon the availability of suitable energy sources.