Small intestine pancreatic enzymes

Not digested by brush border enzymes of the small intestine, pancreatic juices and enzymes... 

HPL has been purified from the pancreatic juice by De Caro et al. [8]. In contrast to most other pancreatic enzymes, which are secreted as proenzymes and further activated by proteolytic cleavage in the small intestine, pancreatic hpase is directly secreted as a 50 kDa active enzyme consisting of 449 amino acid residues including a high mannose or complex-type glycan chain N-hnked to Asn 166. In vitro, the max-... 

In the stomach, pepsin begins the digestion of proteins by hydrolyzing them to smaller polypeptides. The contents of the stomach pass into the small intestine, where enzymes produced by the exocrine pancreas act. The pancreatic proteases (trypsin, chymotrypsin, elastase, and the carhoxypeptidases) cleave the polypeptides into oligopeptides and amino acids. 

AQP10 has only been identified in the small intestine so far and is thought to play a role in hormonal secretion. AQP11 is expressed in kidney, liver, testis and brain, but no function has been found so far. AQP12 has been identified in pancreatic acinar cells, where it is thought to facilitate the release of digestive enzymes into the pancreatic duct. 

There are two main classes of proteolytic digestive enzymes (proteases), with different specificities for the amino acids forming the peptide bond to be hydrolyzed. Endopeptidases hydrolyze peptide bonds between specific amino acids throughout the molecule. They are the first enzymes to act, yielding a larger number of smaller fragments, eg, pepsin in the gastric juice and trypsin, chymotrypsin, and elastase secreted into the small intestine by the pancreas. Exopeptidases catalyze the hydrolysis of peptide bonds, one at a time, fi"om the ends of polypeptides. Carboxypeptidases, secreted in the pancreatic juice, release amino acids from rhe free carboxyl terminal, and aminopeptidases, secreted by the intestinal mucosal cells, release amino acids from the amino terminal. Dipeptides, which are not substrates for exopeptidases, are hydrolyzed in the brush border of intestinal mucosal cells by dipeptidases. 

The absorption efficiency of the different carotenoids is variable. For example, (3-cryptoxanthin has been reported to have higher absorption efficiency than a-cryptoxanthin in rats (Breithaupt and others 2007). Carotenoids must be liberated from the food before they can be absorbed by intestinal cells (Faulks and Southon 2005). Mechanical disruption of the food by mastication, ingestion, and mixing leads to carotenoid liberation (Guyton and Hall 2001). The enzymatic and acid-mediated hydrolysis of carbohydrates, lipids, and proteins (chemical breaking of the food) also contributes to carotenoids liberation from the food matrix (Faulks and Southon 2005). Once released, carotenoids must be dissolved in oil droplets, which are emulsified with the aqueous components of the chyme. When these oil droplets are mixed with bile in the small intestine, their size is reduced, facilitating the hydrolytic processing of lipids by the pancreatic enzymes (Pasquier and others 1996 Furr and Clark 1997 ... 

The pancreas, in which the mucus blocks its ducts in 85 per cent of cystic fibrosis patients, causing pancreatic insufficiency. This is chiefly characterized by secretion of greatly reduced levels of digestive enzymes into the small intestine. 

The presence or absence of pancreatic enzymes can only be satisfactorily decided by intraduodenal intubation and direct examination of samples of small intestinal contents after the administration of a suitable stimulus to pancreatic secretion (Fll). It is not sufficient to look at one enzyme only, such as trypsin, since a specific deficiency of lipase can occur (Sll). Assessment of the degree of hydrolysis of fat in the stools is quite unreliable as a guide to pancreatic enzyme activity (CIO). 

Fats and other lipids are poorly soluble in water. The larger the accessible surface is—i. e., the better the fat is emulsified—the easier it is for enzymes to hydrolyze it (see p. 270). Due to the special properties of milk, milk fats already reach the gastrointestinal tract in emulsified form. Digestion of them therefore already starts in the oral cavity and stomach, where lipases in the saliva and gastric juice are available. Lipids that are less accessible—e.g., from roast pork—are emulsified in the small intestine by bile salts and bile phospholipids. Only then are they capable of being attacked by pancreatic lipase [4] (see p. 270). 

B. Further digestion of carbohydrates by pancreatic enzymes occurs in the small intestine... 

Degradation of dietary nucleic acids occurs in the small intestine, where a family of pancreatic enzymes hydrolyzes the nucleotides to nucleosides and free bases. Inside cells, purine nucleotides are sequentially degraded by specific enzymes, with uric acid as the end product of this pathway. [Note Mammals other than primates oxidize uric acid further to allantoin, which, in some animals other than mammals, may be further degraded to urea or ammonia.]... 

Protein digestion starts in the mouth and continues in your stomach and small intestines. This is due to pepsin, which is secreted in the saliva and obviously the gastric juice, followed by pancreatic enzymes, then absorbed by the mucosal cells in the small intestines. In short, the digestive system breaks down protein into its peptide amino acid structures so they can be absorbed in the small intestine via the... 

The action of the gastric and pancreatic enzymes causes the release of small peptides as well as free amino acids, the peptide fraction being the quantitatively dominant one (9). Thus further hydrolysis is crucial, if the dietary protein is to be completely utilized by the organism. The final stages of hydrolysis is associated with the intestinal mucosal cells. Larger peptides are probably hydrolyzed by enzymes at the brush border membrane. Di- and tripeptides may be absorbed as such and hydrolyzed intracellularly (9, 10). 

Therefore, another possibility in animal studies is to wash out the upper jejunum with a small volume of bicarbonate buffer, and use this fluid as a medium to determine the stability of a test macromolecule or formulation. A similar approach can be used to study enzyme activities in the colon in animals. It should be noted that the preparations should not be centrifuged, but used in their entirety as enzymes can bind to particulate matter or are on the surfaces of bacteria in the case of colon contents (Woodley 1991). Fluid thus obtained from the upper intestine should contain all the pancreatic enzymes, bile salts and sloughed-off cells, but again getting the concentrations right is not obvious. 

The trypsin family of proteases plays a role in acute and chronic pancreatitis, as well as leads to its ultimate destruction [4, 105]. In pancreatitis, active exocrine enzymes are prematurely released inside the pancreatic duct. Various factors can contribute to the development of acute pancreatitis. Trypsinogen, chymotrypsinogen, procarboxypeptidase, and proelastase are inactive proforms of proteolytic enzymes produced by the pancreatic acinar cells. Following secretion these enzymes are activated in a cascade that converts trypsinogen to trypsin in the duodenum and/or small intestine. 

Triglycerides are hydrolyzable into their component fatty adds and glycerol. They are espedally susceptible to alkaline hydrolysis. If KOH or NaOH is used, the process is saponification and the products, sodium and potassium salts of fatty adds, are called soaps. In the human organism, triglycerides are hydrolyzed by various esterases called lipases. These enzymes are quite spedfic, and they do not necessarily remove all three fatty add molecules from a triglyceride molecule. Thus, pancreatic lipase, the main lipid digestive enzyme of the small intestine, catalyzes the removal of fatty acids from positions 1 and 3 only. 

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