Enzymes are bio-catalysts which enhance the rate of a reaction. They convert substrate into related products in the body.
Speed of enzyme reaction decides how fast the body physiology works.
They are very critical in the body as they control some of the important physiological functions.
Specific enzymes control functions like digestion, metabolism, absorption, excretion, penetration, blood clotting and even reproduction.
Unlike hormones, they are released and also act near the site of their production.
Even they are involved in detoxification of drugs and toxins in the body. Also enzymes proteins are targets for drug action.
Enzymes are present in both plants and animals.
Examples of enzymes
- Digestive: Amylase, Trypsin, lypase.
- Metabolic: Oxidase, hydrolases, lygase
- Liver: Serum glutamic oxaloacetic transaminase, Serum glutamic pyruvic transaminase.
- Nucleases: Topoisomerase, endonuclease, DNA polymerase
- Receptor enzymes: These are enzymes which are part of receptor system: Ex:phosphokinases, .
These are a group of enzymes involved in digestion of food in humans and animals. They are
Amylase: Digests carbohydrates to breakdown into glucose.
In-fact carbohydrate digestion begins in the mouth due to salivary amylase. Hence when we chew the food, it turns out to be a bit sweeter than before. This is because, the salivary amylase digests starch into glucose. This glucose imparts sweetness to the taste. The remaining food is digested in stomach and the intestine.
Pepsin, peptidases, Trypsin: Digests proteins into amino acids.
Proteins are complex molecules and they are broken down to some extent in stomach but to a large extent in small intestine.
Lipase: These enzymes digests fats and oils to fatty acids and alcohols for easy absorption.
Nucleases: Breakdown nucleic acids into nucleotides.
The enzymes examples mentioned are present near the gastrointestinal tract.
Receptor enzymes: These enzymes are part of receptors system. They help in many function of the body like activation and inactivation of certain biomolecules like glycogen, glucose etc. The receptors enzymes are of two types like those which help in phosphorylation and dephosphorylation. Those enzymes which help in phosphorylation are called a kinases and those which help in dephosphorylation are called as phosphatases. These types of receptors are classified under kinase linked receptors.
As the name indicates, these are the enzymes which aid in metabolism and also detoxification of substances in body. They are like
- Oxidases: These oxidase substances to alcohols or ketones etc.
- Hydrolases: These breakdown substance by addition of water.
- Reductases: These add hydrogen to a substrates in the reaction.
- Lyases: The enzymes which are involved in breaking of molecules without hydrolysis or oxidation.
- Ligases: Enzymes which brings in bonding of two or more molecules.
- Isomerases: These enzymes convert same molecule from one form to another and vice versa.
- Glucuronidase: This is the key enzyme which adds glucouronic acid to the non-water soluble substances and converts them to water soluble forms to be excreted through urine.
- Transaminases: These are enzymes involved in addition or removal of amino acids.
- Gycogensynthase: This is the enzyme which synthesizes glycogen from glucose to store in liver.
- Aminoacyl tRNA synthetase: This enzyme bind amino-acid to t-RNA.
- Lactate dehydrogenase: Enzymes which converts lactate to pyruvic acid.
Liver enzymes: Liver is an organ of metabolism in the body. It detoxifies almost any substance and helps in expulsion from body through urine. There are many enzymes in liver and few of the important include
1. Serum glutamic oxaloacetic transaminase (SGOT) also called as aspartate aminotransferase (AST).
2. Serum glutamate pyruvate transaminase (SGPT) also called as Alanine transaminase (ALT). Both the enzymes catalyze amino-acids.
Both SGOT and SGPT catalyze reactions involving amino-acids.
Special enzymes in body
- Urokinase: Helps to breakdown clots in the body.
- Hyaluronidase: An enzyme secreted by sperm when released into female reproductive tract. This enzyme helps pierce through ova wall and merge with ova.
- DNA topoisomerase-II: The enzyme which catalyses cutting (nicking) and sealing function on DNA.
- DNA dependent RNA polymerase: An enzyme which helps in formation of mRNA.
- Endonucleases: These are the enzymes which helps in cutting DNA strands. Restriction endonucleases are the type which cut DNA strands at one specific site. These are highly used in genetic engineering.
- Cyclo-oxygenase Enzyme: These enzymes are of two types as COX-1 and COX-II. They regulate synthesis of prostaglanding which are involved in inflammation and gastric mucus production.
These enzymes are present in different animals with different roles. They are
- Hirudin: An enzyme from leech saliva which keep blood flowing without being clotted from the host body. This helps leech suck as much blood as it needs. Hence leech therapy uses them to minimize pain of varicose veins by sucking accumulated blood.
- Autolysin: Enzyme in some bacteria which can auto destroy the cell producing it.