There are hundreds of enzymes in the human body and other living organisms.
Prominent Examples of enzymes in the body include
- 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: They are part of certain types of receptors. Ex: phosphokinases.
- Metalloenzymes: Phosphatases, phosphodiesterases, nitrogenases, oxygenases.
- Restriction enzymes: Sau3A, EcoRI, HindIII
Enzymes, as we know, are the bio-catalysts that enhance the reaction rate of a biochemical reaction.
When a substrate binds to the enzyme’s active site, it becomes a specific product in the body.
The speed of this chemical reaction depends on the catalytic activity of enzymes.
They regulate digestion, metabolism, detoxification of drugs, absorption, excretion, blood clotting, reproduction, and other body physiology.
Examples of enzymes in detail
These are involved in the digestion of food in humans and animals. They are
This enzyme helps in the digestion of carbohydrates. In most cases, they are broken down into glucose.
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 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
They digest proteins. The protein structure is broken down into amino acids.
This helps digest fats and oils to fatty acids and alcohol for easy absorption. It is also one of the pancreatic enzymes.
As the name indicates, they are prominently acting on nucleic acids.
The pancreas releases these nucleases into the small intestine.
They help in the breakdown of DNA and RNA into nucleotides.
It is found in the saliva in the mouth and helps kill foreign microbes. It is also found in the tears of the eye, cell cytoplasm, etc.
These are part of the receptors system. The major enzymes of this system include kinases, phosphatases.
Their activities help in communication in the body. They help in 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 involved in metabolic reactions and detoxify the substances in the body. These include
A) Oxidases: These oxidase substances to alcohols or ketones etc.
Ex: alcohol dehydrogenase.
B) Hydrolases: These are also called hydrolytic enzymes. They help in the breakdown of materials by the addition of water.
Examples; amylase, cellulase.
C) Reductases: These add hydrogen to substrates in the reaction.
D) Lyases: These are involved in breaking molecules without hydrolysis or oxidation.
E) Ligases: These help in the bonding of two or more molecules.
F) Isomerases: They help in the transition of the same molecule from one form to another and vice versa.
G) Glucuronidase 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.
H) Transaminases: These are the ones involved in adding or removing amino acids.
I) Glycogen synthase: This is the one that synthesizes glycogen from glucose to store in the liver.
J) Aminoacyl tRNA synthetase: This helps bind amino-acid to tRNA.
K) Lactate dehydrogenase: It catalyzes the conversion of lactate to pyruvic acid.
L) Fatty acid synthase: It helps synthesize fats in the body.
The liver is an organ of metabolism in the body. It has a few specialized enzymes 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, including a few of the important ones.
- SGOT is also called aspartate aminotransferase (AST).
2. SGPT, also called Alanine transaminase (ALT).
Both of them 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 enzymes (CYP450 enzymes). 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 perfect for others.
Since they are specifically linked with the liver, they help in the diagnosis of liver disease.
These are the ones that have a metallic ion in their structure. This metal ion helps in electron transfer and facilitates biochemical reactions by the enzyme.
These cut the DNA at particular sequences to produce DNA fragments. They are a type of endonucleases.
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: It is secreted by sperm when released into the female reproductive tract. This enzyme helps pierce through the ova wall and merge with the ova.
- DNA topoisomerase-II: This 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.
Interesting enzymes in specific animals
Some enzymes are found exceptionally in some living organisms but absent in others.
They are meant for special functions, as mentioned below.
It is found in the saliva of a leech. The leech sticks to other animal surfaces and sucks the blood.
This enzyme from saliva prevents the clotting of the blood and ensures continuous flow.
Thus leech can suck as much blood as it needs.
Interestingly, this phenomenon of leech enzymes finds use in medicine to help remove accumulated blood in varicose veins.
This is found in some bacteria, which helps in cell division. It destroys the peptidoglycan of the cell wall and facilitates, separation of daughter cells.
Enzymes in snake poison
Snake venom is deadly, and more than 80% of its solid matter is composed of enzyme proteins.
These, when injected directly by bite, can damage the victim’s 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 hemorrhaging: This causes bleeding after a snake bite.
Besides, snake poison also has 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 death.
Thus as seen above, we can find many enzymes in all living organisms. They are used for digestion, food collection, protection from enemies, hunting, etc.
- Leeches can save a life.