Pankreatické enzymy
Chymotrypsin.
- Mr 23,800
- Pure chymotrypsin is an expensive enzyme
- Used only for diagnostic and analytical applications [11]
- Specific for the hydrolysis of peptide bonds
- Carboxyl groups are provided by one of the three aromatic amino acids
- phenylalanine, tyrosine, or tryptophan [11]
- Used extensively in the deallergenizing of milk protein hydrolysates [11]
Healthy individuals
- Cumulative postprandial pancreatic enzyme response
- Exceeds 10- to 15-fold the quantity required to prevent overt maldigestion and malabsorption [5]
- Most important inorganic component of pancreatic juice is bicarbonate
- Increases duodenal pH
- Enhances intraluminal enzyme activities
- All pancreatic enzymes have their pH optima in the alkaline range [5]
Alpha-amylase and lipase
- Secreted into the duodenum in active
Proteases
- Enter the duodenum as inactive zymogens
Pancreatic Exocrine Insufficiency
Příčiny
- Most important causes of pancreatic exocrine insufficiency
- Chronic pancreatitis in adults
- Cystic fibrosis in children [5]
- Secretion of all components of pancreatic juice is affected
- Degree of reduction may vary for individual enzymes [5]
- Other pancreatic causes include:
- Acute necrotizing pancreatitis
- Pancreatic cancer
- Surgery that also lead to loss of functioning pancreatic tissue [5]
- Extrapancreatic disorders can also be associated with pancreatic exocrine insufficiency mostly due to regulatory disturbances
- Celiac disease
- Impaired pancreatic enzyme release in response to a meal
- Reduced cholecystokinin (CCK) release from the diseased mucosa
- Resulting in insufficient prandial stimulation of the pancreas [5]
- Inflammatory bowel disease
- Gastric resections
- Diabetes mellitus
Clinical symptoms
- Steatorrhea
- Decreased availability of lipid-soluble vitamins
- Pancreatic secretory capacity is reduced to less than 5-10% of its normal function [5]
- Bone metabolism may have been underestimated [ 5]
- Moderately impaired pancreatic exocrine insufficiency may contribute to
- Dyspeptic symptoms
- Diarrhea
- Particularly in patients with additional affections of the GIT [5]
Isolated deficiencies of pancreatic enzymes
- May also occure
- Extremely rare
Trypsinogen
- To trypsin by the duodenal enzyme enteropeptidase (i.e. enterokinase)
- Subsequently trypsin exerts an autocatalytic effect
- Activates the other proteases
- Recently suggested to target the enteropeptidase gene as a potential therapeutic option in obesity [5]
Trypsin
- A potent activator of proenteropeptidase that cleaves the zymogen and related synthetic substrate with similar high kcat/Km values
- Duodenase demonstrates a 100-fold lower efficiency toward the same substrates as trypsin
- Duodenase compared to trypsin is generally a ‘slow’ enzyme
- Possesses high selectivity toward substrates
- Duodenase exhibits no activity towards trypsinogen
- Very slowly cleaves the synthetic substrate Gly-(Asp)4-Lys-NA
- Trypsin appears to be a inefficient activator of trypsinogen cleaving it with an extremely low kcat/Km value
- Enteropeptidase, being a natural activator of trypsinogen converts it into active enzyme with very high catalytic efficiency
- Trypsin catalyzes the hydrolysis of only those peptide bonds where
Stimulace sekrece trypsinu
- AMK in the upper part of the intestine (duodenum)
- Release into the blood of thehormone cholecystokinin
- Stimulates secretion of several pancreatic enzymes [15]
Další využití
- Target for biocontrol of insect pests
- Limited applications in the food industry
- protein hydrolysates generated by its action have a highly bitter taste [11]
- Used in the preparation of bacterial media and in some specialized medical applications [11]
