Pig liver esterase, and

In related work, Dong and Martin developed an assay that detects the catalytic activity of the enzymes pig liver esterase and porcine kidney leucine aminopeptidase by using substrates which have been labeled with metal-binding ligands [57], The enzymes catalyze changes in the substrates that affect their ability to bind to non-luminescent Ru complexes to form mixed-ligand complexes capable of ECL. 

Of the many hydrolases known, only the lipases, subtilisin and to some extent a-chymotrypsin, pig liver esterase, and thermolysin[64a) show a sufficiently high... 

Hultin, P C., Mueseler, F.)., and Jones, ).B. (1991) Enzymes in organic synthesis. 48. Pig liver esterase and porcine pancreatic lipase catalyzed hydrolyses of 3,4-(isopropylidenedioxy)-2,5-tetrahydrofuranyl diesters. J. Org. Chem., 56 (18), 5375-5380. 

Related methyl -D-glucopyranosiduronates were made from the acetylated 0-trimethylsilyl glycoside and aldehyde dialkylacetals in the presence of trimethylsilyl triflate. Following deacetylation the products were tested as enzyme substrates, compound (38) giving the free carboxylic acid with pig liver esterase and hydrolysing to release butanol with -D-glucuronidase, the latter illustrating the potential of such substances as releases of cytotoxic aldehydes. ... 

Esterases, proteases, and some lipases are used in stereoselective hydrolysis of esters bearing a chiral or a prochiral acyl moiety. The substrates are racemic esters and prochiral or meso-diesters. Pig liver esterase (PLE) is the most useful enzyme for this type of reaction, especially for the desymmetrization of prochiral or meso substrates. 

Hermann, M., Kietzmann, M.U., Ivancic, M. et al. (2008) Alternative pig liver esterase (APLE) - cloning, identification and functional expression in Pichia pastoris of a versatile new biocatalyst. Journal of Biotechnology, 133 (3), 301-310. 

In a report describing the first enzymatic synthesis of a chiral nonracemic tetraorgano germane, Tacke and coworkers subjected the prochiral cis-hydroxymethyl derivative (10) to acetylation catalyzed by pig liver esterase (Scheme 3)6. The resulting monoacetate (11) was shown to be of 55% ee through 11 NMR analysis of the Mosher ester derivative. 

The indomethacin-hydrolyzing enzyme from pig liver microsomes was purified and partially characterized [60]. The enzyme was found to be different from known pig liver esterases, since it did not hydrolyze naphth-l-yl-acetate and (4-nitrophenyl)acetate, which are typical substrates for these car-boxy lesterases. The amino acid sequence of the enzyme showed high homology with the mouse carboxylesterase isoenzyme ES-male. Human liver car-... 

Fig. 7.5. General formula summarizing the structural and stereochemical requirements, which an ester should meet to fit into the active site of pig liver esterase. A nucleophilic attack by the serine OH group seemingly occurs from this side B no or only small substituents allowed here C groups of small to medium size allowed in this area D space allowed in these areas for carbon chains, with polar substituents (e.g., another ester group) preferred in the upper part ...

Fig. 7.6. Topographical model of the active site of pig liver esterase showing the catalytic OH group and two binding sites (1 and 2) capable of accommodating hydrophobic groups of the substrate. Binding to site 1 is stronger and, thus, dominates until the steric dimensions of the site are exceeded. The model shows two substrates in position, namely dimethyl 3-methylglu-tarate (top) and dimethyl 3-benzylglutarate (bottom), which are hydrolyzed preferentially to the (R)- and (5)-monoester, respectively [68].

Fig. 7.7. Topographical model of the active site of pig liver esterase as proposed by Jones and co-workers [70] [71]. The model postulates two hydrophobic sites, one large (HL) and one small (Hs), and two polar binding sites, one in the front (PF) and one in the back (PB). The serine sphere shows the approximate zone of action of the catalytic OH group, a) A view from the top with the dimensions in A the sites HL, Hs, and PF are at ground level and have an elevation of 3.1 A, 2.3 A, and 1.6 A, respectively, while PB is located 1.5 A above ground level and has an elevation of 0.8 A. b) A computer-generated perspective view with dimethyl phenylmalonate positioned to have its pro-S ester group close to the catalytic site [72a].

Thioesters play a paramount biochemical role in the metabolism of fatty acids and lipids. Indeed, fatty acyl-coenzyme A thioesters are pivotal in fatty acid anabolism and catabolism, in protein acylation, and in the synthesis of triacylglycerols, phospholipids and cholesterol esters [145], It is in these reactions that the peculiar reactivity of thioesters is of such significance. Many hydrolases, and mainly mitochondrial thiolester hydrolases (EC 3.1.2), are able to cleave thioesters. In addition, cholinesterases and carboxylesterases show some activity, but this is not a constant property of these enzymes since, for example, carboxylesterases from human monocytes were found to be inactive toward some endogenous thioesters [35] [146], In contrast, allococaine benzoyl thioester was found to be a good substrate of pig liver esterase, human and mouse butyrylcholinesterase, and mouse acetylcholinesterase [147],... 

P. Mohr, L. Rosslein, C. Tamm, 3-Hydroxyglutarate and f3,y-Epoxy Esters as Substrates for Pig Liver Esterase (PLE) and a-Chymotrypsin , Helv. Chim. Acta 1987, 70, 142 -152. 

J. Boutelje, M. Hjalmarsson, K. Hult, M. Lindback, T. Norin, Control of the Stereoselectivity of Pig Liver Esterase by Different Reaction Conditions in the Hydrolysis of cw-iV-Benzyl-2,5-bismethoxycarbonylpyrrohdine and Structurally Related Diesters , Bioorg. Chem. 1988, 16, 364-375. 

J. B. Jones, R. S. Hinks, P. G. Hultin, Enzymes in Organic Synthesis. 33. Stereoselective Pig Liver Esterase-Catalyzed Hydrolyses of meso Cyclopentyl-, Tetrahydrofuranyl-, and Tetrahydrothiophenyl-1,3-Diesters , Can. J. Chem. 1985, 63, 452-456. 

G. Sabbioni, J. B. Jones, Enzymes in Organic Synthesis. 39. Preparations of Chiral Cyclic Acid-Esters and Bicyclic Lactones via Stereoselective Pig Liver Esterase Catalyzed Hydrolyses of Cyclic meso Diesters ,./. Org. Chem. 1987, 52, 4565 - 4570. 

It is also interesting to note that the three hemiesters of metronidazole are good substrates of pig liver esterases. The ty2 values for hydrolysis of the hemisuccinate, hemiglutarate, and hemimaleinate were 0.2, 2.3, and 2.0 h, respectively, in 5% pig liver homogenate at 37° and pH 7.4. 

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