Enzymes are bio-catalysts which enhance the rate of a reaction. They convert a substrate into related products in the body.
The speed of the enzyme reaction decides how fast the body physiology works.
They are very critical in the body as they control some of the essential 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, lipase.
- Metabolic: Oxidase, hydrolases, lygases, cytochrome -450
- Liver: Serum glutamic oxaloacetic transaminase, Serum glutamic pyruvic transaminase.
- Nucleases: Topoisomerase, endonuclease, DNA polymerase
- Receptor enzymes: These are enzymes which are part of certain types of receptors. Ex: phosphokinases,
These are a group of enzymes involved in digestion of food in humans and animals. They are
Amylase: Digests carbohydrates to break down 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 absorbed in the 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 the stomach but to a large extent in the small intestine.
Lipase: These enzymes digest fats and oils to fatty acids and alcohols for easy absorption. This enzyme is one of the pancreatic enzymes.
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 functions of the body like activation and inactivation of individual 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 kinases and those helping dephosphorylations are called as phosphatases. These receptors are classified under kinase-linked receptors. So few enzymes are also receptors.
As the name indicates, these are the enzymes which aid in metabolism and also detoxification of substances in the body. They are like
- Oxidases: These oxidase substances to alcohols or ketones etc.
- Hydrolases: These breakdown materials by the addition of water.
- Reductases: These add hydrogen to substrates in the reaction.
- Lyases: The enzymes which are involved in breaking of molecules without hydrolysis or oxidation.
- Ligases: Enzymes which brings in a bonding of two or more molecules.
- Isomerases: These enzymes convert the same molecule from one form to another and vice versa.
- Glucuronidase: This is the key enzyme which adds glucuronic acid to the non-water soluble substances and converts them to water-soluble forms to be excreted in urine.
- Transaminases: These are the enzymes involved in the addition or removal of amino acids.
- Glycogen synthase: This is the enzyme which synthesizes glycogen from glucose to store in the liver.
- Aminoacyl tRNA synthetase: This enzyme bind amino-acid to tRNA.
- 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.
Besides them there is a big family of metabolic enzymes named as cytochrome-P 450‘s. They are mainly involved in metabolism of xenobiotics. These enzymes have genetic variations among few American population (hispanics) which leads to variation in drug effects in the body. I.e., the same drug can be toxic or ineffective to one person while it is perfectly good for others.
Enzymes of nervous system: These are the ones which help in metabolism of neurotransmitters.
Ex: 1. Acetyl cholinesterase– breaks down acetyl choline.
2. Monoamine oxidase: Breaks down catecholamines like dopamine, adrenalin and nor-adrenalin.
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.
Interesting enzymes in other animals:
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.
Enzymes in snake poison: Snake venom is deadly and more than 80% of its solid matter is composed of enzymes. These enzymes when injected by bite can lead to damage of victim tissues and organs. These enzymes include
a) Phospholipase A2: It is the most common enzyme in snake venom and it damages mitochondria, blood cells, nerve endings, skeletal muscles etc.
b) DNAase: Can damage DNA of the victim.
c) Zinc metalloproteinase haemorrhagins: This causes bleeding after snake bite.
Besides snake poison also has enzymes like 5’-nucleotidase, Phosphomono- and diesterases, NAD-nucleosidase, l-amino acid oxidase, Peptidases etc.
So as part of first aid, few try to prevent the spread of these enzymes in the body to avoid further damage and the chances of death.
Thus as seen above, we can find many enzymes in nature. They are used for digestion of food, the collection of food, protection from enemies, hunting etc.