A trypsin inhibitor (TI) is a protein and a type of serine protease inhibitor (serpin) that reduces the biological activity of trypsin by controlling the activation and catalytic reactions of proteins. [1] Trypsin is an enzyme involved in the breakdown of many different proteins, primarily as part of digestion in humans and other animals such as monogastrics and young ruminants. Serpins – including trypsin inhibitors – are irreversible and suicide substrate-like inhibitors. [2] [3]
It destructively alters trypsin thereby rendering it unavailable to bind with proteins for the digestion process. [4] As a result, protease inhibitors that interfere with digestion activity have an antinutritional effect. Therefore, trypsin inhibitors are considered an anti-nutritional factor or ANF. [5] Additionally, trypsin inhibitor partially interferes with chymotrypsin function.
Trypsinogen is an inactive form of trypsin, its inactive form ensures protein aspects of the body, such as the pancreas and muscles, are not broken down. It is formed in the pancreas and activated to trypsin with enteropeptidase [6] Chymotrypsinogen is the inactive form of chymotrypsin and has similar functions as trypsin.
The presence of trypsin inhibitor has been found to result in delayed growth as well as metabolic and digestive diseases. [7] Additionally, pancreatic hypertrophy is a common occurrence with trypsin inhibitor consumption [8] The presence of trypsin inhibitor in a product reduces the protein efficiency and therefore results in the consumers body not being able to efficiently and fully utilize the protein. [9]
Trypsin inhibitor is present in various foods such as soybeans, grains, cereals and various additional legumes. [10] The main function of trypsin inhibitors in these foods is to act as a defense mechanism. By having this harmful component wild animals learn that any food that contains trypsin inhibitor is a food to avoid. Trypsin inhibitor can also be essential for biological processes within the plant.
Trypsin inhibitor can also naturally occur in the pancreas of species such as bovines. The function of this is to protect the animal from any accidental activation of trypsinogen and/or chymotrypsinogen [11]
Trypsin inhibitor is heat labile, therefore by exposing these foods to heat, the trypsin inhibitor is removed and the food subsequently becomes safe to eat. [12] Boiling soybeans for 14 minutes inactivates about 80% of the inhibitor, and for 30 minutes, about 90%. At higher temperatures, e.g. in pressure cookers, shorter cooking times are needed. [13] ELISA tests can be used to measure the degree of deactivation achieved.
The most prominent application of trypsin inhibitor is livestock feed. Soybeans are a popular ingredient in livestock feed therefore trypsin inhibitor can be a concern due to the presence of it in soybeans. The majority of soybeans used in livestock feed is converted to soybean meal and through the process the trypsin inhibitor is removed due to the heat treatment. However, experiments have been done concerning animals who consume active trypsin inhibitor and they consistently have decreased weights.
Source | Inhibitor | Molecular weight | Inhibitory power | Details |
---|---|---|---|---|
Blood plasma | α1-antitrypsin | 52 kDa | Also known as serum trypsin inhibitor | |
Lima beans | 8–10 kDa | 2.2 times weight | A mixture of six different inhibitors | |
Bovine pancreas and lung | Aprotinin | 6.5 kDa | 2.5 times weight | Also known as BPTI (basic pancreatic trypsin inhibitor) and Kunitz inhibitor. Best-known pancreatic inhibitor. Inhibits several different serine proteases |
Raw avian egg white | Ovomucin | 8–10 kDa | 1.2 times weight | The ovomucoids are a mixture of several different glycoprotein protease inhibitors |
Soybeans | 20.7–22.3 kDa | 1.2 times weight | A mixture of several different inhibitors. All also bind chymotrypsin to a lesser degree. |
A study revealing that a protease inhibitor from the eggs of the freshwater snail Pomacea canaliculata , interacting as a trypsin inhibitor with the protease of potential predators, was reported in 2010, the first direct evidence for this mechanism in the animal kingdom. [14]
The peptide tumor-associated trypsin inhibitor (TATI) has been used as a marker of mucinous ovarian carcinoma, urothelial carcinoma, and renal cell carcinoma. TATI is metabolised by the kidneys and is, thus, elevated in patients with kidney failure. It may be elevated in non-neoplastic processes such as pancreatitis and can be used as a prognostic marker in this setting (levels above 70 micrograms/L are associated with poor prognosis).
Fifty percent of stage I mucinous ovarian carcinomas are associated with elevated TATI, and nearly 100% of stage IV tumors show elevated TATI.
Eighty-five to 95% of pancreatic adenocarcinomas are associated with increased TATI (but elevation in pancreatitis limits the clinical utility of TATI in this setting; see above).
Sixty percent of gastric adenocarcinomas show elevated TATI, in particular tumors of diffusely infiltrative/signet ring type. TATI, thus, complements CEA, which is elevated exclusively in intestinal type adenocarcinoma of the stomach.
In urothelial carcinoma, TATI expression varies with stage, ranging from 20% in low-stage tumors to 80% of high-stage tumors.
TATI sensitivity in the setting of renal cell carcinoma is approximately 70%. Elevated TATI is more likely to be seen in patients with advanced-stage disease.
In nearly all tumor types studied, TATI is a marker of poor prognosis. [15]
Proteolysis is the breakdown of proteins into smaller polypeptides or amino acids. Uncatalysed, the hydrolysis of peptide bonds is extremely slow, taking hundreds of years. Proteolysis is typically catalysed by cellular enzymes called proteases, but may also occur by intra-molecular digestion.
Trypsin is an enzyme in the first section of the small intestine that starts the digestion of protein molecules by cutting long chains of amino acids into smaller pieces. It is a serine protease from the PA clan superfamily, found in the digestive system of many vertebrates, where it hydrolyzes proteins. Trypsin is formed in the small intestine when its proenzyme form, the trypsinogen produced by the pancreas, is activated. Trypsin cuts peptide chains mainly at the carboxyl side of the amino acids lysine or arginine. It is used for numerous biotechnological processes. The process is commonly referred to as trypsinogen proteolysis or trypsinization, and proteins that have been digested/treated with trypsin are said to have been trypsinized.
The pancreas is an organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdomen behind the stomach and functions as a gland. The pancreas is a mixed or heterocrine gland, i.e., it has both an endocrine and a digestive exocrine function. 99% of the pancreas is exocrine and 1% is endocrine. As an endocrine gland, it functions mostly to regulate blood sugar levels, secreting the hormones insulin, glucagon, somatostatin and pancreatic polypeptide. As a part of the digestive system, it functions as an exocrine gland secreting pancreatic juice into the duodenum through the pancreatic duct. This juice contains bicarbonate, which neutralizes acid entering the duodenum from the stomach; and digestive enzymes, which break down carbohydrates, proteins and fats in food entering the duodenum from the stomach.
A protease is an enzyme that catalyzes proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the formation of new protein products. They do this by cleaving the peptide bonds within proteins by hydrolysis, a reaction where water breaks bonds. Proteases are involved in numerous biological pathways, including digestion of ingested proteins, protein catabolism, and cell signaling.
In biochemistry, a zymogen, also called a proenzyme, is an inactive precursor of an enzyme. A zymogen requires a biochemical change for it to become an active enzyme. The biochemical change usually occurs in Golgi bodies, where a specific part of the precursor enzyme is cleaved in order to activate it. The inactivating piece which is cleaved off can be a peptide unit, or can be independently-folding domains comprising more than 100 residues. Although they limit the enzyme's ability, these N-terminal extensions of the enzyme or a "prosegment" often aid in the stabilization and folding of the enzyme they inhibit.
Serpins are a superfamily of proteins with similar structures that were first identified for their protease inhibition activity and are found in all kingdoms of life. The acronym serpin was originally coined because the first serpins to be identified act on chymotrypsin-like serine proteases. They are notable for their unusual mechanism of action, in which they irreversibly inhibit their target protease by undergoing a large conformational change to disrupt the target's active site. This contrasts with the more common competitive mechanism for protease inhibitors that bind to and block access to the protease active site.
Serine proteases are enzymes that cleave peptide bonds in proteins. Serine serves as the nucleophilic amino acid at the (enzyme's) active site. They are found ubiquitously in both eukaryotes and prokaryotes. Serine proteases fall into two broad categories based on their structure: chymotrypsin-like (trypsin-like) or subtilisin-like.
Chronic pancreatitis is a long-standing inflammation of the pancreas that alters the organ's normal structure and functions. It can present as episodes of acute inflammation in a previously injured pancreas, or as chronic damage with persistent pain or malabsorption. It is a disease process characterized by irreversible damage to the pancreas as distinct from reversible changes in acute pancreatitis. Tobacco smoke and alcohol misuse are two of the most frequently implicated causes, and the two risk factors are thought to have a synergistic effect with regards to the development of chronic pancreatitis. Chronic pancreatitis is a risk factor for the development of pancreatic cancer.
Digestive enzymes take part in the chemical process of digestion, which follows the mechanical process of digestion. Food consists of macromolecules of proteins, carbohydrates, and fats that need to be broken down chemically by digestive enzymes in the mouth, stomach, pancreas, and duodenum, before being able to be absorbed into the bloodstream. Initial breakdown is achieved by chewing (mastication) and the use of digestive enzymes of saliva. Once in the stomach further mechanical churning takes place mixing the food with secreted gastric acid. Digestive gastric enzymes take part in some of the chemical process needed for absorption. Most of the enzymatic activity, and hence absorption takes place in the duodenum.
Trypsinogen is the precursor form of trypsin, a digestive enzyme. It is produced by the pancreas and found in pancreatic juice, along with amylase, lipase, and chymotrypsinogen. It is cleaved to its active form, trypsin, by enteropeptidase, which is found in the intestinal mucosa. Once activated, the trypsin can cleave more trypsinogen into trypsin, a process called autoactivation. Trypsin cleaves the peptide bond on the carboxyl side of basic amino acids such as arginine and lysine.
Carcinoembryonic antigen (CEA) describes a set of highly-related glycoproteins involved in cell adhesion. CEA is normally produced in gastrointestinal tissue during fetal development, but the production stops before birth. Consequently, CEA is usually present at very low levels in the blood of healthy adults. However, the serum levels are raised in some types of cancer, which means that it can be used as a tumor marker in clinical tests. Serum levels can also be elevated in heavy smokers.
Enteropeptidase is an enzyme produced by cells of the duodenum and is involved in digestion in humans and other animals. Enteropeptidase converts trypsinogen into its active form trypsin, resulting in the subsequent activation of pancreatic digestive enzymes. Absence of enteropeptidase results in intestinal digestion impairment.
The drug aprotinin, is a small protein bovine pancreatic trypsin inhibitor (BPTI), or basic trypsin inhibitor of bovine pancreas, which is an antifibrinolytic molecule that inhibits trypsin and related proteolytic enzymes. Under the trade name Trasylol, aprotinin was used as a medication administered by injection to reduce bleeding during complex surgery, such as heart and liver surgery. Its main effect is the slowing down of fibrinolysis, the process that leads to the breakdown of blood clots. The aim in its use was to decrease the need for blood transfusions during surgery, as well as end-organ damage due to hypotension as a result of marked blood loss. The drug was temporarily withdrawn worldwide in 2007 after studies suggested that its use increased the risk of complications or death; this was confirmed by follow-up studies. Trasylol sales were suspended in May 2008, except for very restricted research use. In February 2012 the European Medicines Agency (EMA) scientific committee reverted its previous standpoint regarding aprotinin, and has recommended that the suspension be lifted. Nordic became distributor of aprotinin in 2012.
Maspin is a protein that in humans is encoded by the SERPINB5 gene. This protein belongs to the serpin superfamily. SERPINB5 was originally reported to function as a tumor suppressor gene in epithelial cells, suppressing the ability of cancer cells to invade and metastasize to other tissues. Furthermore, and consistent with an important biological function, Maspin knockout mice were reported to be non-viable, dying in early embryogenesis. However, a subsequent study using viral transduction as a method of gene transfer was not able to reproduce the original findings and found no role for maspin in tumour biology. Furthermore, the latter study demonstrated that maspin knockout mice are viable and display no obvious phenotype. These data are consistent with the observation that maspin is not expressed in early embryogenesis. The precise molecular function of maspin is thus currently unknown.
Ulinastatin is a glycoprotein that is isolated from healthy human urine or synthetically produced and has molecular weight of 25 - 40kDa. It acts as a urinary trypsin inhibitor (UTI). Highly purified ulinastatin has been clinically used for the treatment of acute pancreatitis, chronic pancreatitis, Stevens–Johnson syndrome, burns, septic shock, and toxic epidermal necrolysis (TEN).
Trypsin-1, also known as cationic trypsinogen, is a protein that in humans is encoded by the PRSS1 gene. Trypsin-1 is the main isoform of trypsinogen secreted by pancreas, the others are trypsin-2, and trypsin-3 (meso-trypsinogen).
Pancreatic secretory trypsin inhibitor (PSTI) also known as serine protease inhibitor Kazal-type 1 (SPINK1) or tumor-associated trypsin inhibitor (TATI) is a protein that in humans is encoded by the SPINK1 gene.
Kunitz soybean trypsin inhibitor is a type of protein contained in legume seeds which functions as a protease inhibitor. Kunitz-type Soybean Trypsin Inhibitors are usually specific for either trypsin or chymotrypsin. They are thought to protect seeds against consumption by animal predators.
Protease, serine, 2 is a protein that in humans is encoded by the PRSS2 gene.
Protease, serine, 3 is a protein that in humans is encoded by the PRSS3 gene.
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