Carboxyl ester lipase function

Hui DY, Howies PN. Carboxyl ester lipase structure-function relationship and physiological role in lipoprotein metabolism and atherosclerosis. J Lipid Res2002 43 2017-2030. 

The most important and typical enzymes that function at lipid-water interfaces in micelles, liposomes, emulsions, etc., are lipases. Lipases are carboxylic ester hydrolases and have been termed glycerol ester hydrolases (EC3.1.1.3) in the international system of classification. They differ greatly as regards both their origins (bacterial, fungal, plant, mammalian, etc.) and their properties, and they can catalyze the synthesis as well as the hydrolysis of a wide range of different carboxylic esters. Numerous reports have appeared about the structure and function of pancreatic lipases, because they are ubiquitous in mammalian species and play important roles in dietary fat absorption [29,30]. In this part, I will describe a structural feature and its relation to catalytic mechanism at the interfaces of lipases, particularly pancreatic lipases. 

End-functional polymers were also synthesized by lipase-catalyzed polymerization of DDL in the presence of vinyl esters [103,104]. The vinyl ester acted as terminator ( terminator method ). In using vinyl methacrylate (12.5 mol % or 15 mol % based on DDL) and lipase PF as terminator and catalyst, respectively, the quantitative introduction of methacryloyl group at the polymer terminal was achieved to give the methacryl-type macromonomer (Fig. 12). By the addition of divinyl sebacate, the telechelic polyester having a carboxylic acid group at both ends was obtained. 

Lipases are enzymes of the hydrolase family and, in nature, hydrolyze fatty acid esters in aqueous environment. It is worth recalling that the hydrolysis of esters is a reversible reaction. Chemists thus often use lipases to catalyze the reverse reaction, i.e., the esterification and the ROP of lactones. In 1993, the groups of Kobayashi [91] and Knani [92] reported independently the hpase-catalyzed ROP of sCL and 8-valerolactone. The aliphatic polyesters were functionalized by a carboxylic group at one chain-end and a hydroxyl group at the other chain-end. Accordingly, the polymerization was initiated and terminated by water present in the reaction media. 

Lipase catalysts have been used for functionalization of polymers. A terminal hydroxy group of poly-(e-CL) was reacted with carboxylic acids using lipase CA catalyst to give end-functionalized polyesters.231 Lipase MM catalyzed the regioselective transesterification of the terminal ester group of oligo (methyl methacrylate) with allyl alcohol.232 In the PPL-catalyzed reaction of racemic 2,2,2-trichloroethyl 3,4-epoxybutanoate with hydroxy-terminated PEG, the... 

It is possible to resolve amino acids through either the amino or carboxylate functionality. If salt formation is the method employed, then usually the corresponding functionality in the substrate is protected or masked to avoid interference. The more common approach is to use an enzyme such as an esterase or lipase to hydrolyze just one enantiomer of an ester or amide substrate (Scheme... 

The mechanism of amide- and ester-hydrolyzing enzymes is very similar to that observed in the chemical hydrolysis by a base. A nucleophilic group from the active site of the enzyme attacks the carbonyl group of the substrate ester or amide. This nucleophilic chemical operator can be either the hydroxy group of a serine (e.g., pig fiver esterase, subtifisin, and the majority of microbial lipases), a carboxyl group of an aspartic acid (e.g., pepsin) [3], or the thiol functionality of cysteine (e.g., papain) [4-6]. 

Since the introduction of WS-3, many other coolants have appeared on the market, mostly based on the menthol structure and, in fact, synthesized from menthol. These are shown in Fig. 8.45. Three menthyl esters are produced. The lactate (201) is made by Symrise and sold under the trade name Frescolat ML, while the succinate (202) is available from Advanced Biotech as Koolada. Menthyl pyrrohdone carboxylate (203) is sold by Quest as Questice. Questice serves as a sustained release precursor for menthol, the ester function being cleaved by lipases. It therefore finds use in cosmetics since the release rate is affected by the moisture levels in the skin. Thus as the body tries to lose heat, e.g., on exercise, Questice provides the desirable sensation of cooling. Some higher menthyl esters have been patented as coolants by Firmenich (259). Two menthyl ethers are also of interest as coolants. The mono- ether of propylene glycol (204) has been added to the FEMA/GRAS list and the monoglyceryl ether (205) is sold as... 

The enzymatic deprotection principle has also been applied in solid phase synthesis to create an anchoring structure that contains two cleavable positions an allylic ester on the one hand and a hydrophilic ester on the other hand. The release of j ptide using a palladium(O) catalyst delivers the peptide that is still bound to the hydrophilic structure. The carboxylic function can be liberated [48] using lipase catalysts (Fig. 32). This strategy was successfully demonstrated in the solid phase synthesis of peptides as well as O- and iV-glycopeptides [48]. 

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