Liver esterase

Esterases Liver, blood Other tissues Soluble fraction of cells... 

One approach called enzymatic resolution, involves treating a racemic mixture with an enzyme that catalyzes the reaction of only one of the enantiomers Some of the most commonly used ones are lipases and esterases enzymes that catalyze the hydrol ysis of esters In a typical procedure one enantiomer of the acetate ester of a racemic alcohol undergoes hydrolysis and the other is left unchanged when hydrolyzed m the presence of an esterase from hog liver... 

Eig. 3. Enzyme-catalyzed resolutions. PLE = pig liver esterase. See text. 

Porcine liver esterase (PLE) gives excellent enantioselectivity with both dimethyl 3-methylglutarate [19013-37-7] (lb) and malonate (2b) diester. It is apparent from Table 1 that the enzyme s selectivity strongly depends on the size of the alkyl group in the 2-position. The hydrolysis of ethyl derivative (2c) gives the S-enantiomer with 75% ee whereas the hydrolysis of heptyl derivative (2d) results in the R-monoester with 90% ee. Chymotrypsin [9004-07-3] (CT) does not discriminate glutarates that have small substituents in the 3-position well. However, when hydroxyl is replaced by the much bulkier benzyl derivative (Ic), enantioselectivity improves significantly. 

PPL = porcine pancreatic lipase PLE = porcine liver esterase. 

Pig liver esterase is particularly effective in cleaving one ester of a symmetrical pair. 

Chirazymes. These are commercially available enzymes e.g. lipases, esterases, that can be used for the preparation of a variety of optically active carboxylic acids, alcohols and amines. They can cause regio and stereospecific hydrolysis and do not require cofactors. Some can be used also for esterification or transesterification in neat organic solvents. The proteases, amidases and oxidases are obtained from bacteria or fungi, whereas esterases are from pig liver and thermophilic bacteria. For preparative work the enzymes are covalently bound to a carrier and do not therefore contaminate the reaction products. Chirazymes are available form Roche Molecular Biochemicals and are used without further purification. 

A synthesis of the important biosynthetic intermediate mevalonic acid starts with the enzymatic hydrolysis of the diester A by pig liver esterase. The pro-R group is selectively hydrolyzed. Draw a three-dimensional structure of the product. 

This group was designed as an enzymatically cleavable protective group. Cleavage is achieved using an esterase present in mouse plasma or hog liver carboxylate esterase. " ... 

Levofloxacin (6) was enantioselectively obtained by the enzymatic hydrolysis of ofloxacin butyl ester by immobilization of porcine liver esterase (01MI25, 01MI32). 

Chifdl rraildple-coupLing reageats have beea prepared in enandomerically pure form by enando-selecdve saporuficadon of diesters of meso-2-nitrQcyclohexane-1,3-diols fEq. 3.44 widi pig liver esterase fPLEi. ... 

Table 1.1 Influence ofcosolvents on the asymmetric hydrolysis the prochiral diester (1) catalyzed by pig liver esterase. of...

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. 

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