Substrate pancreatic lipase

Malakhova, E.A., Kurganov, B.I., Levashov, A.V., Berezin, I.V., Martinek, K. 1983. A new approach to the study of enzymatic reactions with the participation of water-insoluble substrates. Pancreatic lipase enclosed in inverted micelles of surface-active substances in an organic solvent. Dokl. Akad. Nauk. SSSR 270,474 77. 

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. ... 

Within the small intestine, bile-acid binding interferes with micelle formation. Nauss et al. [268] reported that, in vitro, chitosan binds bile acid micelles in toto, with consequent reduced assimilation of all micelle components, i.e., bile acids, cholesterol, monoglycerides and fatty acids. Moreover, in vitro, chitosan inhibits pancreatic lipase activity [269]. Dissolved chitosan may further depress the activity of lipases by acting as an alternative substrate [270]. 

Goldstein, N. P. Epstein, J. H. and Roe, H. J. Studies of pancreatic function IV. A simplified method for determination of pancreatic lipase using aqueous tributyrin as substrate, with one hundred normal values by this method. J. Lab. Clin. Med. (1948), 33, 1047-1051. 

In 1958 Sarda and Desnuelle [79] discovered the lipase activation at the interfaces. They observed that porcine pancreatic lipase in aqueous solution was activated some 10-fold at hydrophobic interfaces which were created by poorly water-soluble substrates. An artificial interface created in the presence of organic solvent can also increase the activity of the lipase. This interfacial activation was hypothesized to be due to a dehydration of the ester substrate at the interface [80], or enzyme conformational change resulting from the adsorption of the lipase onto a hydrophobic interface [42,81,82]. 

Some of the pancreatic enzymes in the lumen include pancreatic amylase, pancreatic lipase, elastase, trypsin, a-chymotrypsin, and carboxypeptidase A. For example, the aspirin derivatives aspirin phenylalanine ethyl ester, aspirin phenyllactic ethyl ester, and aspirin phenylalanine amide have been studied as substrates for carboxypeptidase A [67,68], with the phenylalanine ethyl ester derivative proving to be the best substrate. This study indicated that the carboxypeptidase A may serve as a reconversion site for many drug derivatives. 

A further group of AT-[(acyloxy)methyl] pro-moieties contains acidic and/or lipid-like substituents. Here again, most published results concern phenytoin. Thus, some phenytoin-lipid conjugates such as 8.183 and 8.186 (with R = various fatty acyl moieties) were reported [233]. Such prodrugs are, of course, insoluble in water but formed dispersions when briefly sonicated in EtOH/water mixtures containing sodium taurodeoxycholate. No significant hydrolysis was seen in buffer or plasma. In contrast, incubation with pancreatic lipase yielded the bis-deacyl derivatives (i.e., 8.182 and 8.185, respectively), with subsequent liberation of phenytoin the time for 50% liberation of phenytoin varied from 20 to 200 min under the conditions of the studies [233][234], The intermediates 8.182, 8.184, and 8.185 were also substrates for human and rat plasma hydrolases. 

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. 

Hydrolases, which catalyze the hydrolysis of various bonds. The best-known subcategory of hydrolases are the lipases, which hydrolyze ester bonds. In the example of human pancreatic lipase, which is the main enzyme responsible for breaking down fats in the human digestive system, a lipase acts to convert triglyceride substrates found in oils from food to monoglycerides and free fatty acids. In the chemical industry, lipases are also used, for instance, to catalyze the —C N —CONH2 reaction, for the synthesis of acrylamide from acrylonitril, or nicotinic acid from 3-pyridylnitrile. 

The kinetic results for the lipase-catalysed enantioselective hydrolysis of the esters (236)-(240) can be interpreted in terms of frontier orbital localization.213 The porcine pancreatic lipase (PPL)-mediated optical resolution of 18 racemic esters can be explained by a mechanistic model involving a W-shaped active conformation of the substrate lying in a diastereo-discriminating plane.214... 

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. 

Pancreatic carboxytester lipase, secreted by the pancreas as an active enzyme without proteolytic activation, displays broad substrate specificity and has therefore received many names in the literature carboxylesteraae, bile salt-stimulated (or activated or dependent) lipaae (due to its absolute requirement for bile salts to hydrolyze insoluble substrates), carbaxylester lipase or hydrolase, cholesterol... 

It is dear that the interconnection between the activities of the different lipolytic enzymes, where the first enzyme modifies the physicochemical state of the lipid substrate in such a way that it becomes available to another enzyme, is not only of prime importance for lipid digestion, but also results in a broad synergism between gastric lipase, colipase, pancreatic lipase, phospholipase As. calcium, caiboxylester Lipase, bite salts, and substrate interraecK tes [55,62-64]. 

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). 

The increased lability of diisopropyl acetals resulting from their steric compression1 lft is useful for retrieving aldehydes in sensitive substrates, A synthesis of Lipstatin [Scheme 2.55], a powerful pancreatic lipase inhibitor used in the treatment of obesity, required conditions for the deprotection of fJ-rm-butyldi-methylsilyloxy aldehyde intermediate 55.5 without competing -elimination.117... 

Enzymes are active in organic solvents at low water contents. Porcine pancreatic lipase in glycerin tributyrate (tributyrin) shows, for 0.015% water in the tributyrin—pentanol reaction mixture, a rate of transesterification comparable to the value in aqueous solution (Klibanov, 1986 Zaks and Klibanov, 1984). The water content of the protein in the above reaction mixture was 0.01—0.03 h. This is below the level expected for the onset of enzyme activity in protein—water powders. Nonaqueous solvents can produce change in the substrate specificity of an enzyme (Zaks and Klibanov, 1986 Zaks and Klibanov, 1988a) and possibly can lock the enzyme into a more active conformation (Russell and Klibanov, 1988). The dependence of the catalytic activity on added water has been measured for several enzymes in several solvents (Zaks and Klibanov, 1988b). 

Pancreatic lipase can be considered a model for all other lipases. Most if not all of these enzymes seem to be nonspecific carboxyl ester hydrolases of the serine histidine type. Their specificity consists, by definition, in their ability to hydrolyze insoluble substrates, but apart... 

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