Specificity of pancreatic lipase

Jensen, R. G., Sampugna, J. and Pereira, R. L. 1964. Intermolecular specificity of pancreatic lipase and the structural analysis of milk triglycerides. J. Dairy Sci. 47, 727-732,... 

H, BrockerhofF, Substrate specificity of pancreatic lipase influence of the structure of forty adds cm the reactivity of esters. Bbdiin. Biophys. Acta 212 92 (1970). 

These experiments confirm and extend the observations made on a simple model system. Of the lipolytic products, the least soluble in bile acid solutions are fatty acids. Monoglyceride and soap have much higher solubilities, indicating that the formation of a clear micellar phase is enhanced in vivo by alkahnization (from pancreatic bicarbonate) or by having an appreciable fraction of fatty acid present as monoglyceride (which occurs because of the positional specificity of pancreatic lipase). 

Mattson, F. H., and L. W. Beck The specificity of pancreatic lipase for the primary hydroxyl groups of glycerides. J. biol. Chem. 219, 735 (ifefi). 

Brockerhoff, H. (1970) Substrate specificity of pancreatic lipase influence... 

Porcine pancreatic lipase catalyzes the transesterification reaction between tribu-tyrin and various primary and secondary alcohols in a 99% organic medium (Zaks, 1984). Upon further dehydration, the enzyme becomes extremely thermostable. Not only can the dry lipase withstand heating at 100 °C for many hours, but it exhibits a high catalytic activity at that temperature. Reduction in water content also alters the substrate specificity of the lipase in contrast to its wet counterpart, the dry enzyme does not react with bulky tertiary alcohols. 

The sensitivity and specificity of these tests are limited by the complexity of the processes of absorption and metabolism. The substrates are specific for pancreatic lipases and the product is absorbed independently of micelle formation, but the results of the test are affected by other factors, such as gastric emptying, mucosal absorption, hepatic metabolism, endogenous "CO2, and total CO2 production. These factors may explain the test s limited diagnostic sensitivity in mild and moderate pancreatic insufficiency and its lack of specificity in nonpancreatic GI diseases. 

Topical pancreatic lipase substrates like tributyrin and triolein emulsions are hydrolyzed by carboxylester lipase in the presence of bile salt but slowly—at a rate lower than 3% and 0.5%, respectively, of that observed with the lipase-colipase complex. On the other hand, the positional specificity is not restricted all three sn positions of triglycerides can be split by the carboxylester lipase. While long-chain phospholipids are resistant, short-chain phospholipids are readily attacked by carboxylester lipase [40]. The low substrate specificity of carboxylester lipase makes possible an essential role for this enzyme in the hydrolysis of triglycerides containing certain esterified polyunsaturated fatty acids, such as eicosapentaenoic, arachidonic, or linoleic acids [41], and which may be resistant to attack by pancreas lipase (see p. 190). 

Inhibition of Lipid Absorption - Agents which decrease the absorption of dietary lipids specifically by inhibiting pancreatic lipase may be suitable for the treatment of obesity. The reduced rate of lipid absorption produced by fenfluramine in rats is probably due to an inhibition of pancreatic lipase. The structural features of a series of phenethylamines, including fenfluramine, required for lipase inhibition have been described using partially purified rat and human pancreatic lipase. Pluronic L-101, a hydrophobic surfactant is a potent inhibitor of pancreatic lipase vitro and reduces body weight gain and carcass lipid after chronic administration to rats. Fecal excretion of dietary lipid is enhanced by Pluronic L-101, thus supporting its action as a lipase inhibitor. 

It was generally assumed that oxidation products from oils and fats are poorly absorbed. Indeed, animals can be resistant to the effects of abused oils in their diet (29,30). Nevertheless, orally administered oxidized C-linoleic acid was incorporated into chylomicrons and very low density lipoprotein (VLDL) particles in rats. The absorbed oxidation products were subsequently identified as hydroxy fatty acids (31). Interestingly, dietary glutathione (GSH) reduced the absorption of peroxidized linoleate (32), presumably due to the activity of selenium-dependrait GSH peroxidase present in the intestinal epithelial cell (33). However, these absorption studies used free fatty adds, not triglycerides thus, they cannot address the role of pancreatic lipase and phospholipase. The fate of polymerized fatty adds has not been studied specifically. Whether the intestinal flora could degrade fliese polymers and hence allow their absorption remains to be seen. What is clear is that very little is known about the absorption of oxidized fat in animals and even less in humans. 

The pancreatic lipase immunoreactivity (PLI) assay is a measure of lipase and its related precursors. While the function of pancreatic lipase is the same as any other lipase in the body, the molecular structure is unique. For this reason, a radioimmunoassay (RIA) and subsequently an enzyme-linked immunosorbent assay (ELISA) were developed and validated by the Westbrook, ME, US-based manufacturer, IDEXX Laboratories, Inc., for dogs and cats to measure canine and feline PLI (i.e., cPLI and fPLI, respectively). Relative to TLl, species-specific PLI assays have better sensitivity and specificity for detection of pancreatitis (Xenoulis, 2015). Based upon the available data, PLI appears to be the most sensitive laboratory test available for the diagnosis of pancreatitis. Although rat-reactive commercial PLI antibody is available, there is as yet a significant need to develop and validate an ELISA assay that can reliably detect the antigen in preclinical species. 

Other biochemists presented evidence that there is a true gastric lipase that in its substrate specificity differs from both lingual and pancreatic lipase. Fritz Schon-heyder and Kirsten Volqvartz of Aarhus determined the substrate specificity of a lipase they found in gastric contents recovered from the stomachs of adult human subjects 25 minutes after the subjects had eaten a meal. Only lower triglycerides, they found, were split while the meal was in the stomach. In vitro the pH optimum of the enzyme depended upon the nature of the substrate, being 5.5 to 5.8 for tri-propein, tributyrin, and tricaproin but 7.0 to 7.9 for tricaprin, trilaurin, and tri-stearin. ... 

Hydrolysis products are dependent on the specificity of lipase. In the case of pancreatic lipase, the final products are fatty acids and 2-monoacylglycerols, in the case of s -non-specific hpases from... 

Candida cylindracea, phosphate buffer pH 7, Bu20. The 6-0-acetyl of Q -methyl peracetylglucose was selectively removed. Porcine pancreatic lipase will also hydrolyze acetyl groups from carbohydrates. These lipases are not specific for acetate since they hydrolyze other esters as well. In general selectivity is dependent on the ester and the substrate. ... 

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). 

Selected entries from Methods in Enzymology [vol, page(s)] Detergent-resistant phospholipase Ai from Escherichia coll membranes, 197, 309 phospholipase Ai activity of guinea pig pancreatic lipase, 197, 316 purification of rat kidney lysosomal phospholipase Ai, 197, 325 purification and substrate specificity of rat hepatic lipase, 197, 331 human postheparin plasma lipoprotein lipase and hepatic triglyceride lipase, 197, 339 phospholipase activity of milk lipoprotein lipase, 197, 345. 

Pancreatic lipase has been found to be strictly sn 1,3-specific, that is the primary fatty acid esters of the triglyceride. Although the two primary hydroxyl groups on... 

Abstract The major enzymatic barrier to the absorption of macromolecules, particularly therapeutic peptides, is the pancreatic enzymes the peptidases, nucleases, lipases and esterases that are secreted in considerable quantities into the intestinal lumen and rapidly hydrolyse macromolecules and lipids. In the case of the peptidases, they work in a co-ordinated fashion, whereby the action of the pancreatic enzymes is augmented by those in the brush borders of the intestinal cells. The sloughing-off of mucosal cells into the lumen also furnishes a mixture of enzymes that are a threat to macromolecules. As the specificity and activity of the enzymes are not always predictable, during pharmaceutical development it is important to test the stability of therapeutic macromolecules, and novel macromolecular-containing or lipid-containing formulations, in the presence of mixtures of pancreatic enzymes and bile salts, or in animal intestinal washouts or ideally, aspirates of human intestinal contents. 

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