We can find many examples of enzymes in the human body with diverse functions.
Prominent Examples of enzymes in the body are
- Digestive enzymes: Amylase, Trypsin, lipase.
- Metabolic enzymes: Oxidase, hydrolases, ligases, cytochrome -450
- Liver enzymes: Serum glutamic oxaloacetic transaminase (SGOT), Serum glutamic pyruvic transaminase (SGPT).
- Nucleases: Topoisomerase, endonuclease, DNA polymerase
- Receptor enzymes: These are enzymes that are part of certain types of receptors. Ex: phosphokinases,
Enzymes as we know are the bio-catalysts that enhance the rate of a biochemical reaction.
They help convert a substrate into a specific product in the body. The speed of the enzyme reaction decides how fast the body physiology works.
Enzymes are very critical to the body physiology as they control some of the essential functions.
Specific enzymes control processes 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 the 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 in detail
These are a group of enzymes involved in the digestion of food in humans and animals. They are
Amylase: This enzyme helps in the digestion of carbohydrates. In most cases, they are broken down into glucose.
The 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 alcohol for easy absorption. This enzyme is one of the pancreatic enzymes.
As the name indicates, they are prominently acting on the nucleic acids. These enzymes are released by the pancreas into the small intestine. They help in the breakdown of DNA and RNA into nucleotides.
Lysozyme is another enzyme that is found in the cell cytoplasm. It is also present in the saliva of the mouth to kill the microbes.
The above-mentioned enzymes examples are released into the gastrointestinal tract.
Receptor enzymes: These enzymes are part of the receptors system. The major examples of enzymes of this system include kinases, phosphatases. They help in many body functions related to the activation and inactivation of individual biomolecules like glycogen, glucose, etc. These receptors act so by either phosphorylation or dephosphorylation. Those enzymes which help in phosphorylation are called kinases and those involved in dephosphorylations are called phosphatases. These receptors are classified under kinase-linked receptors. So few enzymes are also receptors.
As the name indicates, these are the enzymes that 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 that bring in the 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 that adds glucuronic acid to the non-water-soluble substances and converts them to water-soluble forms to be excreted in the urine.
- Transaminases: These are the enzymes involved in the addition or removal of amino acids.
- Glycogen synthase: This is the enzyme that 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.
The liver is an organ of metabolism in the body. It has a few specialized enzymes in it for the purpose.
The liver detoxifies almost any substance and helps in expulsion from the body through urine. There are many enzymes in the liver and a few of the important include
1.SGOT is also called as aspartate aminotransferase (AST).
2. SGPT also called 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 cytochrome-P 450s. They are mainly involved in the metabolism of xenobiotics.
These enzymes have genetic variations among the few American populations (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 the nervous system: These are the ones that help in the metabolism of neurotransmitters.
Ex: 1. Acetylcholinesterase– breaks down acetylcholine.
2. Monoamine oxidase: Breaks down catecholamines like dopamine, adrenalin, and nor-adrenalin.
Special enzymes in the body
- Urokinase: Helps to breakdown clots in the body.
- Hyaluronidase: An enzyme secreted by sperm when released into the female reproductive tract. This enzyme helps pierce through the ova wall and merge with ova.
- DNA topoisomerase-II: The enzyme which catalyzes cutting (nicking) and sealing function on DNA.
- DNA dependent RNA polymerase: An enzyme that helps in the formation of mRNA.
- Endonucleases: These are the enzymes that help in cutting DNA strands. Restriction endonucleases are the type that 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 the synthesis of prostaglandins which are involved in inflammation and gastric mucus production.
You can also check out: The important function of enzymes.
Other Interesting enzymes in specific animals:
These are examples of enzymes present in different animals. They are
- Hirudin: An enzyme from leech saliva which keeps 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 the 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 to 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 the DNA of the victim.
c) Zinc metalloproteinase haemorrhagins: This causes bleeding after a snake bite.
Besides snake poison also has enzymes like 5’-nucleotidase, Phosphomono- and di esterase, 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.