Collegedunia Team Content Curator
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Proteolytic enzymes are the enzymes that break down proteins into amino acids. They are essential for the digestion of proteins in our body. Proteolytic enzymes are also called proteases, peptidases and proteinases. They break down proteins by hydrolyzing peptide bonds between the amino acids.
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Key Takeaways: Proteolytic Enzymes, Amino Acids, Exopeptidases, Endopeptidases, Trypsin, Chymotrypsin, Carboxypeptidase, Pepsin, Aminopeptidase
Types of Proteolytic Enzymes
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Proteolytic enzymes work by acting on a particular site in a protein. Depending upon the bond or site they cleave, proteolytic enzymes are broadly classified into two main categories:
Exopeptidases
Exopeptidases include those proteolytic enzymes which act upon the terminal ends of a protein molecule. As a result of their action, single amino acids or monomer units can be obtained. Exopeptidases are also termed as dipeptidases. Carboxypeptidase and aminopeptidase fall under the category of exopeptidases.
Proteolytic Enzyme
Endopeptidases
Endopeptidases include those proteolytic enzymes that cleave the peptide bonds present within the protein molecules at non-terminal ends. This type of cleavage gives short peptide chains instead of monomer units. Endopeptidases include pepsin, trypsin, chymotrypsin etc.
Exopeptidases and Endopeptidases
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Sources of Proteolytic Enzymes
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Proteolytic enzymes can be obtained from the following sources:
Human Body
Naturally, proteolytic enzymes are produced in the body by the stomach and pancreas. The main types of proteolytic enzymes produced in the body are trypsin, pepsin and chymotrypsin. These enzymes convert the protein present in our food into smaller units that can be easily absorbed by the body.
Food Sources
The proteolytic enzymes can also be obtained from some food sources. The main sources of proteolytic enzymes are papaya and pineapple.
Papaya contains the proteolytic enzyme called papain. It is present in the roots, leaves and fruit of the papaya plant. Pineapple contains the proteolytic enzyme bromelain. Other than papaya and pineapple, the dietary sources of proteolytic enzymes include;
- Yoghurt
- Kiwi
- Asparagus
- Ginger
Supplements
Supplements of proteolytic enzymes are also available in the form of tablets, powder, capsules etc. These supplements may contain a specific proteolytic enzyme or a combination of different enzymes. The enzymes used to make the supplements are extracted from natural sources like plants and animals.
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Benefits of Proteolytic Enzymes
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The main function of the proteolytic enzyme is to facilitate digestion of proteins and convert them into smaller units to be absorbed by the body. But there are several other health benefits associated with them.
- Proteolytic enzymes improve digestion by helping in the breaking down of proteins.
- It is also believed that proteolytic enzymes help in reducing inflammation and its symptoms.
Benefits of Proteolytic Enzymes
- Consuming proteolytic enzyme supplements also help in healing the wounds.
- These enzymes may also help in reducing symptoms like gas, constipation, abdominal pain etc. associated with irritable bowel syndrome (IBS).
- Consuming proteolytic enzyme supplements may help in reducing muscle soreness post workout.
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Things to Remember
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- Proteolytic enzymes refer to those groups of enzymes that break down proteins into amino acids.
- Exopeptidases act on the terminal ends of a protein molecule and give amino acid monomers.
- Endopeptidases act on the peptide bonds present within the protein molecule and produce peptide chains.
- Proteolytic enzymes are secreted by the stomach and pancreas in the body.
- Proteolytic enzyme supplements help in reducing inflammation and healing wounds.
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Sample Questions
Ques. State the role of pancreatic juice in digestion of proteins. (3 marks) [NCERT]
Ans. Enzymes like trypsinogen, chymotrypsinogen and procarboxypeptidase are present in the pancreatic juice in their inactive form. These enzymes are activated by other enzymes in the body. Trypsinogen is activated by an enzyme enterokinase into trypsin. Trypsin in turn activates other enzymes of the pancreatic juice. Chymotrypsinogen is activated into chymotrypsin and procarboxypeptidase into carboxypeptidase. These proteolytic enzymes act on proteins, peptones and proteoses present in the chyme and convert them into oligopeptides and dipeptides.
Ques. Describe the process of digestion of protein in the stomach. (3 marks) [NCERT]
Ans. The gastric glands present in the stomach secrete gastric juice. Gastric juice contains HCl and proenzymes - pepsinogen and prorennin. HCl present in the gastric juice converts pepsinogen into its active form pepsin. Pepsin acts on the protein in the stomach and converts them into proteoses and peptones.
The gastric juice of infants contains an inactive enzyme prorennin. Prorennin is activated by pepsin into rennin. Rennin helps in the digestion of casein, a protein present in milk.
Ques. What would happen if HCl were not secreted in the stomach? (3 marks) [NCERT]
Ans. HCl plays a very important role in digestion in our body. It is secreted by the parietal or oxyntic cells of gastric glands. The main functions of HCl are given below:
- HCl activates pepsinogen and prorennin into their active form pepsin and rennin. Pepsin and rennin are the chief proteolytic enzymes present in the stomach. If these enzymes are not activated, digestion of proteins will not take place.
- Its acidic nature kills harmful bacteria present in the food.
- It provides the acidic pH (pH 1.8) optimal for the functioning of pepsin in the stomach.
Ques. Discuss the main steps in the digestion of proteins as the food passes through different parts of the alimentary canal. (5 marks) [NCERT]
Ans. The digestion of proteins begins in the stomach and continues in the intestine. The steps of the digestion of protein in the body are given below:
In Stomach - The cells of the gastric glands in the stomach secrete inactive enzymes pepsinogen and prorennin. Pepsinogen and prorennin are converted into their active form pepsin and rennin by the action of HCl. Pepsin and rennin are the chief proteolytic enzymes present in the stomach. They break down proteins into proteoses and peptones.
In Small Intestine - The peptones and proteoses present in the chyme are then digested in the small intestine by enzymes of pancreatic and intestinal juice. The pancreatic juice contains the proteolytic enzymes - trypsinogen, chymotrypsinogen and procarboxypeptidase. The enterokinase present in the intestinal juice converts inactive trypsinogen into active trypsin. Trypsin in turn activates chymotrypsinogen and procarboxypeptidase into chymotrypsin and carboxypeptidase respectively.
The intestinal juice contains aminopeptidases and dipeptidases which convert large peptides into dipeptides and amino acids.
Amino acids are the final product of protein digestion. They are absorbed by the cells of the intestine.
Ques. What are some functions of proteolytic enzymes? (3 marks)
Ans. Proteolytic enzymes are essential for the digestion of proteins in our body. But they perform other functions too which are:
- They participate in the process of blood coagulation.
- They are also involved in processes like cell division, apoptosis, growth etc.
- They are involved in the activation of zymogens and precursor proteins.
- The help in regulating the process of metastasis, inflammation, tumour growth etc.
- They also help in healing the wounds.
Ques. What are amino acids and their types? (3 marks)
Ans. Amino acids are the monomer units of a protein molecule. Proteins are complex molecules made up of amino acids. There are 20 different amino acids having different structure and function. The amino acids are mainly divided into two categories:
- Essential Amino Acids - It includes those amino acids that are not synthesised in our body. These amino acids are obtained through the food we eat. The essential amino acids are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.
- Non - Essential Amino Acids - It includes those amino acids that can be synthesised by our body. Even if they are not obtained through the food we eat, the body can produce them on their own. The non - essential amino acids are: alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine and tyrosine.
Ques. What are the properties of amino acids? (5 marks)
Ans. The physical and chemical properties of amino acids are as follows:
Physical Properties
- They are colourless, crystalline solids.
- They have a very high melting point.
- They are easily soluble in water.
- Except glycine, all the amino acids are optically active.
Chemical Properties
- Amino acids are a good example of zwitterions. The -NH2 group is a strong base that takes up a H+ ion from the -COOH group and forms a zwitterion with net zero charge.
- Due to the presence of amine and carboxylic groups, they act as both acid and base. Thus, amino acids are amphoteric in nature.
- To detect the presence of aromatic amino acids in a protein solution, xanthoproteic test is performed.
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