Pancrea juice containing

The best explored mammalian phospholipase Az is the type 114 kDa pancreatic enzyme released as a proenzyme. Tike 14 kDa phospholipases have been clafr-siiied utilizing evolutionary relationships into type i (in pancreas juice), type D (in platelets, synovial fluid), and type lH (in bee venom). Platelets and macrophages contain intracellulariy a structurally different 85 kDa phospholipase type IV. 

Depending on nutrient intake, the human pancreas secretes about 3 L of alkaline juice per day. Pancreatic juice contains hydrolytic enzymes... 

A common duct from the pancreas and gall bladder enters the duodenum. Duodenal pH is 6 to 6.5 due to the presence of bicarbonate that neutralizes the acidic ch5une emptied from the stomach. The pH is optimum for enzymatic digestion of protein and peptide food. Pancreatic juice containing enzymes is secreted into the duodenum from the bile duct. Trypsin, ch5unotrypsin, and carboxypeptidase are involved in the hydrolysis of proteins into amino acids. Amylase is involved in the digestion of carbohydrates. Pancreatic lipase secretion hydrolyzes fats into fatty acids... 

The pancreatic juice is released through the ampulla of Vater into the duodenum to aid in the digestive process as well as buffer acidic fluid released from the stomach (Fig. 20-1). The pancreas contains a trypsin inhibitor to prevent autolysis. 

Exocrine glands within the pancreas secrete an aqueous fluid referred to as pancreatic juice. This fluid is alkaline and contains a high concentration of bicarbonate ion it is transported to the duodenum by the pancreatic duct. 

The pancreas of all mammals so far investigated contain an elastase with similar enzymatic reactions (Lewis et al., 1956 Marrama et al., 1959), but immunological differences have been observed between pancreatic elastases from different species (Moon and Mclvor, 1960). Elastase is secreted in the pancreatic juice as an inactive zymogen, proelastase (Grant and Robbins, 1955 Lamy and Lansing, 1961) which, like other pancreatic enzymes, is activated by trypsin or enterokinase. 

In 1936, Anson (127) crystallized what is now called carboxypeptidase A from autolyzed bovine pancreas and noted that fresh pancreas did not contain the active enzyme, but an inactive precursor now named procarboxypeptidase A. It has been reported in the preceding sections that pancreatic juices of other species also contain large amounts of procarboxypeptidase A which can be separated by chromatography on DEAE-cellulose at pH 8.0 in a buffer of increasing molarity. 

Porcine pancreas and porcine pancreatic juice appear to contain a single protein endowed with lipolytic activity. As stated earlier, this protein corresponds to about 2.5 % of the total proteins of the juice. Its molecular activity (turnover number) is likely to be higher than 300,000 under the conditions of the test. Shortage of pure material has thus far prevented any investigation of its molecular properties. It is merely known to be quite soluble in water, to have an isoelectric point of 5.2 in 0.025 M acetate buffer, and to give a conventional protein spectrum. Lipase present in pancreatic juice is likely to be identical with the enzyme extracted from pancreatin. 

The gut contains a collection of nerves called the enteric nervous system. Various activities of the gut, such as peristaltic contractions, and certain activities of the pancreas and gall bladder, are controlled in a manner that is relatively independent of the central nervous system. The central nervous system consists of the brain and spinal cord. Five type,s of activity are controlled by the enteric nervous system (1) contraction of smooth muscles that create the peristaltic waves used to mix and propel food through the intestines (2) release of juices by secretory cells (5) release of hormones from endocrine ceils of the gut (4) patterns of blood flow through the arteries of the gut (variations in blood flow occur because of the opening of blood vessels (vasodilation) or the dosing of blood vessels (vasoconstriction)] and (5) activities of immune cells of the gut (GoyaI and Hirano, 1996). 

Saliva and pancreatic juice both contain a-amylase. The activity of this enzyme in saliva is not significant compared with that in the pancreatic juice released into the gut. Release of amylase from the pancreas is controlled by a mechanism similar or identical to the one that stimulates the release of tr)rpsinogen, namely by the influence of CCK on the exocrine pancreas. Amylase catalyzes the hydrolysis of starch at interior positions rather than at the ends of the polymer. This activity yields products such as maltose and longer-chain-length oligomers of glucose. Also, amylase does not catalyze the hydrolysis of starches at branching points. Therefore, small branched-chain structures called dextrins are formed that are not hydrolyzed by the er zyme. 

Enzyme-rich pancreatic juice which contains several enzymes capable of hydrolysing triacylglycerides and other lipids is secreted from the pancreas and mixed with the chyme. Pancreatic phospholipase Ag hydrolyzes phospholipid, thus producing fatty acids and lyso-phospholipids. Pancreatic triacylglyceride... 

The pancreas possesses both endocrine and exocrine fnnctions. The islets of Langerhans, which contain the cells of the endocrine pancreas, secrete insnlin, glncagon, somatostatin, and other polypeptide hormones. The exocrine pancreas is composed of acini that secrete about 1 to 2 L/day of isotonic fluid that contains water, electrolytes, and pancreatic enzymes necessary for digestion. Bicarbonate is secreted primarily by the centroacinar (ductular) cells, and is the principal ion of physiologic importance. Pancreatic juice is delivered to the duodenum via the pancreatic ducts (Fig. 39-1) where the alkaline secretion (pH about 8.3) neutralizes gastric acid and provides an appropriate pH for maintaining the activity of pancreatic enzymes."... 

The acidic gastric juice enters the duodenum, the upper part of the small intestine, where digestion continues. Secretions from the exocrine pancreas (approximately 1.5 liters/day) flow down the pancreatic duct and also enter the duodenum. These secretions contain bicarbonate (HC03 ), which neutralizes the acidic pH of stomach contents, and digestive enzymes, including pancreatic a-amylase. 

In the earlier experiments by Fischer and Bergell it was found that leucyl-alanine was hydrolysed by an extract of pancreas it was not however hydrolysed by pure pancreatic juice. Such extracts probably contain other enzymes, more especially the autolytic enzyme, which produce the hydrolysis the later work of Abderhalden and his coworkers upon the action of enzymes from various organs also show that polypeptides not hydrolysed by pure tiypsin are attacked by these enzymes (see table, p. 48). 

---