Pancreas phospholipase

The actions of U-II are mediated by a G protein-coupled receptor referred to as the UT receptor. UT receptors are widely distributed in the brain, spinal cord, heart, vascular smooth muscle, skeletal muscle, and pancreas. Some effects of the peptide including vasoconstriction are mediated by the phospholipase C, IP3-DAG signal transduction pathway. 

In the duodenum, dietary lipids are degraded by pancreatic enzymes triacylglycerol by pancreatic lipase, phospholipids by phospholipase A2 and lysophospholipase, and cholesteryl esters by cholesterol esterase. Enzyme release from the pancreas is controlled by cholecystokinin, produced by cells in the intestinal mucosa. 

I various subcellular locations within eukaryotic cells. Some of these enzymes are specific for particular polar head-groups others are nonspecific. Phospholipase A2 is a major component of snake venom (cobra and rattlesnake) and is partially involved in the deadly effects of these venoms. Because of the high concentration of phospholipase A2 in these venoms, this enzyme has been studied intensively. The pancreas is also rich in phospholipase A2, which is secreted into the intestine for digestion of dietary phospholipids. 

Phospholipase A2 catalyzes the hydrolysis of the 2-acyl linkage of all phospholipids. It is secreted as a zymogen by the pancreas, and converted to the active enzyme via a specific tryptic cleavage of the Arg-Ala link which removes an N-terminal heptapeptide from the proenzyme. Phospholipase A2 is one example of the way in which the metabolism of phospholipids is sensitive to calcium at several key points. 

Kinkaid, A. and Wilton, D.C. 1991. Comparison of the catalytic properties of phospholipase A2 from pancreas and venom using a continuous fluorescence displacement assay. Biochem. J. 278, 843-848. 

In vitro, urotensin II is a potent constrictor of vascular smooth muscle its activity depends on the type of blood vessel and the species from which it was obtained. Vasoconstriction occurs primarily in arterial vessels, where urotensin II can be more potent than endothelin 1, making it the most potent known vasoconstrictor. In vivo, urotensin II has complex hemodynamic effects, the most prominent being regional vasoconstriction and cardiac depression. The extent to which the peptide is involved in the regulation of vascular tone and blood pressure in humans is not clear recent studies have produced conflicting results. The actions of urotensin II are mediated by G protein-coupled receptors that are widely distributed in the brain, spinal cord, heart, vascular smooth muscle, skeletal muscle, and pancreas. Some effects of the peptide including vasoconstriction are mediated by the phospholipase C/IP3/DAG signal transduction pathway. 

H7. Hietaranta, A., Kemppainen, E., Puolakkainen, P., Sainio, V., Haapiainen, R., Peuravuori, H., Kivilaakso, E., and Nevalainen, T., Extracellular phospholipases A2 in relation to systemic inflammatory response syndrome (SIRS) and systemic complications in severe acute pancreatitis. Pancreas 18, 385-391 (1999). 

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. 

Relevant quality control should not be restricted to the usual triad of activities of pancreas lipase, a-amylase, and trypsin, but should be extended to the content of colipasc, the activities of the two other lipolytic enzymes present in pancreatine (phospholipase Aj and carboxylester lipase), and the dissolution characteristics of enteric-coated preparations as a function of time and pH (Fig. 16). The availability of such information will certainly contribute to a better tailoring of flic management of maldigestion in the individual patient and to a more appropriate correction of the obligate nonphysio logical route of delivery of these enzyme supplements. 

G. de Haas, N. Postern . W. Nwuwcnhuizen, and L. Van Deenen. Purification and properties of phospholipase A from porcine pancreas. Biochim. Bkrphys. Acta 759 103(1968). 

Lipases are enzymes that hydrolyse triglycerides in fats and phospholipases, as the name indicates, hydrolyse phospholipids. Lipases remove long-chain fatty acids from triglycerides, and they are also frequently described as having esterase activity. There are also specific esterases described in the GI tract, for example, carboxylesterase that is secreted by the pancreas. These enzymes are included in the discussion because their activity may be relevant to the use of macromolecular materials in novel formulations, particularly for oral peptide and nucleic acid delivery. 

Our knowledge of porcine pancreatic phospholipase comes from the laboratory of G. H. de Haas and his co-workers. The enzyme is quite different from pancreatic lipase (Table VIII). Its molecular weight is quite small, it is a metalloenzyme that requires Ca ion as a cofactor, and it is excreted from the pancreas as a proenzyme which is then activated by trypsin with removal of a heptapeptide. The molecule has six... 

Lin, G., Noel, J., Loffredo, W., Stable, H. Z., and Tsai, M.-D. (1988). Use of short-chain cyclopentano-phosphatidylcholines to probe the mode of activation of phospholipase A2 from bovine pancreas and bee venom.y. Biol. Chem. 263, 13208-13214. 

Puijk, W. C., Verheij, H. M., and de Haas, G. H. (1977). The primary structure of the phospholipase As from porcine pancreas A reinvestigation. Biochim. Biophys. Acta 492, 254-259. 

Renetseder, R., Brunie, S., Dijkstra, B. W., Drenth, J., and Sigler, P. B. (1985). A comparison of the crystal structures of phospholipase As from bovine pancreas and Crotalus atrox venom.y. Biol. Chem. 260, 11627—11634. 

Phospholipase Pig s Pancreas Modified Egg Yolk Emulsifying Expression in Yeast Protein Engineering... 

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... 

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