Nicotinamide Adenine Dinucleotide is abbreviated as NAD. It reacts with dehydrogenase enzyme and converts to NADH2 by accepting or releasing hydrogen from the compound.

Reduced Flavin Adenine Dinucleotide is abbreviated as FADH2.

Flavin Adenine Dinucleotide is abbreviated as FAD. It reacts with the dehydrogenase enzyme and converts to FADH2 by accepting or releasing hydrogen from the compound.

When the prosthetic group of the conjugated enzyme is formed by any biochemical substance, it is called co-enzyme. Some of the co-enzymes are-
1. FAD : Flavin Adenine Dinucleotide is abbreviated as FAD. It reacts with the dehydrogenase enzyme and converts to FADH2 by accepting or releasing hydrogen from the compound.
2. FADH2 : Reduced Flavin Adenine Dinucleotide is abbreviated as FADH2.
3. FMN: Flavin Mono Nucleotide is abbreviated as FMN.
4. NAD : Nicotinamide Adenine Dinucleotide is abbreviated as NAD. It reacts with dehydrogenase enzyme and converts to NADH2 by accepting or releasing hydrogen from the compound.
5. NADP : Nicotinamide Adenine Dinucleotide Phosphate is abbreviated as NADP. It reacts with the enzyme dehydrogenase and releases or accepts hydrogen from the compound to NADPH2.
6. NADPH2 : Reduced Nicotinamide Adenine Dinucleotide Phosphate is abbreviated as NADPH2.
7. CO-A : Co-enzyme A is abbreviated as CO-A. CO-A is composed of vitamin B, pyrophosphate and adenylic acid. It regulates fatty acid metabolism, citric acid cycle, sterol and acetyl choline synthesis.
8. ATP : Adenosine Triphos phate is abbreviated as ATP. It provides energy for various metabolic processes.
9. ADP: Adenosine Diphosphate is abbreviated as ADP. ADP and Pi combine to form ATP.
10. Cytochrome: Cytochrome is a type of CoA. It participates in the electron transport system. It participates in carbohydrate metabolism.

Enzymes are composed of globular type proteins. The basic building blocks of proteins are amino acids. Enzymes can contain 62-2,500 different amino acids. Enzymes that are made up of only proteins are called simple enzymes. Many enzymes contain other components besides protein. Enzymes that are composed of protein and non-protein parts are called conjugated enzymes. The protein part of the conjugated enzyme is called the apo-enzyme and the non-protein part is called the prosthetic group. The apo-enzyme and the prosthetic group together are called holoenzymes. A co-factor if the prosthetic group is formed of a metal and a co-factor if it is formed of an organic chemical substance.

Enzymes that are secreted in the active state are called zymase. Tylin is a zymase enzyme. Enzymes that are secreted in inactive form are called zymogens. The inactive enzyme is converted to active enzyme in the presence of some metal ions. Enzyme activity increases in the presence of metal ions are called metal activators. Activating metals are – Mn++, K+, Mg++, Ca++, Zn++ etc. Pepsinogen and trypsinogen are enzymes of zymogen nature.

1. Enzymes are made up of carbon, hydrogen, oxygen, nitrogen and sulphur.
2. All enzymes are proteins.
3. Amino acids that make up proteins are the basic building blocks of enzymes. The amino acid number and sequence of a specific enzyme is specific.
4. It exists in small amounts in chemical reactions.
5. High temperature (50-100°C) and exposure to ultraviolet rays destroy enzyme activity.
6. It is active in both acid and alkaline environment.
7. The enzyme is soluble in water, glycerol and mild alcohol.
8. Enzyme is degraded by ammonium sulphate, sodium chloride, picric acid etc.
9. Enzyme reactions can be unidirectional and bidirectional.
10. Enzyme action is accelerated in the presence of co-enzymes and co-factors.
11. The size of the substrate is smaller than the size of the enzyme.
12. Enzyme contains phosphorus, copper, zinc, iron, manganese, magnesium etc.

1. An enzyme is a type of protein.
2. It stays in cells as colloid.
3. It speeds up the rate of chemical reactions and remains unchanged at the end of the reaction.
4. Enzymes are thermosensitive, meaning enzyme activity increases with increasing temperature. Enzyme at 35-40 degrees C. Most effective at temp.
5. Enzyme activity is controlled by pH. All enzymes are most active at pH 5-9.
6. Enzyme activity is specific, that is, specific enzymes act on specific substrates.
7. Enzyme molecules are larger than substrate molecules.
8. Enzymes are large molecules with high molecular weight.
9. Enzyme activity is related to substrate concentration.
10. Exposure to strong light (ultraviolet rays) destroys enzyme activity.
11. Enzymes are produced only in living cells and require water to function.
12. The activity of enzymes is determined by their three dimensional structure.
13. Enzymes are produced only in living cells. It requires water to function.
14. It is soluble in water, glycerol and mild alcohol.

Physical characteristics of Enzyme
1. An enzyme is a type of protein.
2. It stays in cells as colloid.
3. It speeds up the rate of chemical reactions and remains unchanged at the end of the reaction.
4. Enzymes are thermosensitive, meaning enzyme activity increases with increasing temperature. Enzyme at 35-40 degrees C. Most effective at temp.
5. Enzyme activity is controlled by pH. All enzymes are most active at pH 5-9.
6. Enzyme activity is specific, that is, specific enzymes act on specific substrates.
7. Enzyme molecules are larger than substrate molecules.
8. Enzymes are large molecules with high molecular weight.
9. Enzyme activity is related to substrate concentration.
10. Exposure to strong light (ultraviolet rays) destroys enzyme activity.
11. Enzymes are produced only in living cells and require water to function.
12. The activity of enzymes is determined by their three dimensional structure.
13. Enzymes are produced only in living cells. It requires water to function.
14. It is soluble in water, glycerol and mild alcohol.

Chemical characteristics of Enzyme
1. Enzymes are made up of carbon, hydrogen, oxygen, nitrogen and sulphur.
2. All enzymes are proteins.
3. Amino acids that make up proteins are the basic building blocks of enzymes. The amino acid number and sequence of a specific enzyme is specific.
4. It exists in small amounts in chemical reactions.
5. High temperature (50-100°C) and exposure to ultraviolet rays destroy enzyme activity.
6. It is active in both acid and alkaline environment.
7. The enzyme is soluble in water, glycerol and mild alcohol.
8. Enzyme is degraded by ammonium sulphate, sodium chloride, picric acid etc.
9. Enzyme reactions can be unidirectional and bidirectional.
10. Enzyme action is accelerated in the presence of co-enzymes and co-factors.
11. The size of the substrate is smaller than the size of the enzyme.
12. Enzyme contains phosphorus, copper, zinc, iron, manganese, magnesium etc.

In 1752, scientist Rene Reamur first observed the action of digestive juices on food. In 1825, the scientist Berzelus observed that some substances produced by cells act as organic catalysts. Diastase enzyme was first discovered by French chemists Persoz and Payen in 1833. German physiologist Wilhelm Kuhne first used the term enzyme in 1878. In 1897, German scientist Edward Buchner identified zymase enzyme from sugar. For this he won the Nobel Prize in 1907. In 1926 scientist James B. Sumner) discovered urease enzyme from plant cells. Enzymes, he noted, are made up of proteins. Scientist John H. Northrop (1930-1935) crystallized pepsin, trypsin and chymotrypsin. Scientist Wendell M. Stanley (1930-1935) isolated the TMV protein.