Endopeptidase, also known as endoproteinase, is basically proteolytic peptidases that split peptide bonds in the molecules of non-terminal amino acids. It is just the opposite of exopeptidases that split peptide bonds from the terminal amino acid end pieces. This is the reason why endopeptidase is unable to degrade peptides into monomers. On the other hand, exopeptidases are able to degrade proteins into monomers. Oligopeptidase is a specific example of endopeptidase. The substrates of oligopeptidase comprise oligopeptides and not proteins.
In fact, endopeptidases are a class of protease belonging to a vast family of enzymes that breaks down proteins in ingested foods. Enzymes are basically proteins which help reactions to occur faster than normal. Proteins are made up of amino acid chains that are connected to one another by peptide bonds. Such connections bind one amino acid's carboxyl terminus with that of the next amino acid. Endopeptidases break the amino acids' peptide bonds inside protein molecules. On the other hand, exopeptidases split such linkages at the protein molecule terminals.
Endopeptidases are present in organisms belonging to all classes. In addition, they perform an array of biological functions. These proteolytic peptidases play a vital role in digesting the protein in ingested foods. Such proteins include various enzymes like chymotrypsin, pepsin and trypsin. Proteases also have a function in cellular signalling and they facilitate the process of degrading other proteins such as hormones or antibodies. Moreover, proteases are also able to turn on or turn off.
Initially, proteases are generally made in the form of large inactive molecules. This helps to defend the cells synthesizing proteases from any kind of damage. After the proteases have been supplied to their target, for example the stomach, a small fragment of the molecule is taken away. This molecule piece actually works to make the protease active.
As proteases play a wide assortment of roles in the normal functioning of the cells, the medical community has expressed much interest in the activities of endopeptidase. One such example of the growing medical interest is prolyl endopeptidase, which especially cleaves after the amino acid called proline. This amino acid is known to be related to various psychological disorders like mania, depression and even schizophrenia. Similarly, prolyl endopeptidase inhibitors are also of great medical interest because it is regarded as a potential anti-depressant remedy.
In fact, prolyl endopeptidase is major and large cytosolic enzyme belonging to a separate serine peptidase class. When it was discovered, prolyl endopeptidase was found in the rabbit brain's cytosol in the form of an oligopeptidase that breaks down the non-peptide known as bradykinin present in the Pro-Phe bond. This enzyme plays an important role in breaking down peptides hormones as well as neuropeptides.
Neutral endopeptidase is another good example of protease. Neutral endopeptidase is also known by many other names. It is also referred to as the common acute lymphoblastic antigen or CALLA in short. At the same time, it is also called neprilysin. This particular protease breaks down small unseen peptides comprising those that are said to be responsible for Alzheimer's disease as well as many other vital signalling peptides. Sometimes, this protease is also employed to detect cancer. However, the role of neutral endopeptidase as a cancer marker is yet to be ascertained. Scientists have now developed inhibitors to help in alleviating pain as well as regulating hypertension (high blood pressure).
Different types of endopeptidase belong to different protease families, subject to their active site structure and their preferred conditions. For instance, one family of endopeptide belongs to the serine family, which contain an amino acid called serine at the protease's active site. Endopeptidases belonging to the serine family include proteases involved in the digestive process, such as chymotrypsin and trypsin, in addition to prolyl endopeptidase. One of these endopeptidase inhibitors is highly toxic and is often used for research in biochemical laboratories. This toxic compound is known as phenylmethanesulfonylflouride (PMSF). This endopeptidase inhibitor is utilized in the process of isolating and purifying protein to slow down the activity of serine protease. This is important because serine protease has the ability to break down proteins which are being purified.
On the other hand, there is a sulphur group at the active site of cystine proteases, which is generally found in fruits. In addition, cystine proteases are also present in meat tenderizers. One good example of papain endopeptidase is papain, which is found in elevated amounts in papaya. This enzyme is often used for treating stings by bees and wasps. Usually, aspartic proteases' active site has two aspartate groups and hence the name. Similarly, a metal cofactor is needed by metalloendopeptidates to become active. As neutral endopeptides also belong to this family, they need zinc for their activity.
Understanding chymotrypsin is very important. Basically, this endopeptidase is an enzyme involved in the digestive process. It works to degrade protein molecules in our intestines. The synthesis of chymotrypsin takes place in the form of a relatively large molecule inside the pancreas and is subsequently moved from their as an inactive enzyme. When the inactive chymotrypsin reaches the small intestine, a different digestive enzyme called trypsin activates it.
Digestion of ingested food entails degradation of the big molecules into smaller molecules, which our blood stream can take up and assimilate. Proteins comprise amino acid chains that are connected with one another via peptide bonds. Proteins are actually enzymes that speed up the pace of various cellular reactions, while proteases degrade the proteins. There are various different types of proteases that are involved in the digestion process and they work on different types as well as areas of proteins.
Chymotrypsin is a class of protease belonging to the family called serine proteases, which are also referred to as endopeptides. This type of protease has been named such as they enclose the amino acid serine in their dynamic site. In fact, the synthesis of this protease is done in an inert and larger form that enables serine to be carried to their place of activity ensuring that no damage is caused to any tissues.
Chymotrypsin belongs to the family of serene proteases, which are also called serine endopeptides. These proteases have derived their name from the amino acid serine that is found at their active site. Similar to various other endopeptides, the synthesis of serine proteases also occurs in the form of inactive and relatively large molecules enabling their transportation to their target site or place of activity, while ensuring no damage is done to the tissues. When chymotrypsin is in an inactive form, it is called chymotrypsinogen.
A segment of chymotrypsinogen is cleaved following a restricted proteolysis by trypsin forming a combination of two-molecule chymotrypsin. In this case, the two molecules formed by the proteolysis of chymotrypsinogen activate one another. In addition, these two molecules can also serve as a catalyst in degrading proteins. Chymotrypsinogen prefers to act on specific amino acid types. This endopeptide has a tendency to break down peptide bonds by employing tyrosine, tryptophan or phenylalanine. All of them are aromatic amino acids and have been named such because their internal structure is like a cyclic ring.
The mechanism involved in chymotrypsin involves hydrolysis. This process splits a water molecule into two parts and adds each of them to different segments of the peptide bond, resulting into the cleavage of the bond. After the protein has split by the protease, it continues to be broken down further by other proteases as well as peptides till the protein degraded to amino acids. Once the breakdown of protein is total, the enzymes are inactivated by a group of naturally forming serine protease inhibitors known as serpins.
There are several plants that produce chymotrypsin inhibitors. Generally, protease inhibitors are especially produced by legume seeds and they may serve to protect the plants from insects that absorb their nutrient content. These inhibitors work to restrict the amount of nutrients robbed by the invading insects. In addition, several bacteria present in the human intestine also make protease inhibitors with a view to shield themselves from digestive enzymes and let them stay alive and not be digested.
The activities of chymotrypsin as well as trypsin are medically examined to check pancreatic deficiency and cystic fibrosis. Usually, these two enzymes are present in the stool. Further tests are suggested in case these enzymes are not found in the stool.