Lipases lipid coating

Bio-imprinting of enzymes to enhance their enantioselectivity is thus fairly established. This is particularly useful for enzymes which inherently offer low enantioselectivity, e.g. lipases. Okahata and co-workers established that lipid coating of lipases enhances the solubility of the enzymes in organic media [24]. Subsequently, the technique was extended to phospholipase D for transphosphotidylation of water insoluble phospholipids in organic solvents and to jS-o-galactosidase for the... 

RESULTS ON ENANTIOSELECTIVE ESTER SYNTHESIS USING LIPID COATED BIO-IMPRINTED LIPASE OF IN ANHYDROUS ISO-OCTANE ... 

In some instances, water may not be necessary at all for the solubilization of the enzyme in a hydrocarbon solvent. A striking example has been provided by Okahata and coworkers [78] who solubilized lipase in benzene or n-hexane by coating the enzyme with the nonionic surfactant (24) or 2Ci6Br. The lipid-coated lipase showed activity for the synthesis of di- and triglycerides from monoglycerides and aliphatic acids. 

They suggested that at the higher pressures (and therefore higher dielectric constants), the scCHFg was capable of dissolving more displaced water this would affect enantioselectivity if one substrate enantiomer displaces more water from the enzyme pocket than does the other enantiomer (26). They also noted that SCCO2 inhibited the reaction. A -Acetyl-L-phenylalanine esters are used as detoxins in rice production (87). Mori et al. (27) evaluated the effect of SCCHF3 pressure on the esterification of racemic phenylethanol [Eq. (10)] with a lipid-coated lipase ... 

Mori T, Funasaki M, Kobayashi A, Okahata Y. Reversible activity changes of a lipid-coated lipase for enantioselective esterification in supercritical fluoroform. Chem Commun, 2001 1832-1833. 

Okahata, Y. and Ijiro, K., A lipid-coated lipase as a new catalyst for triglyceride synthesis in organic solvents, J. Chem. Soc. Chem. Comm., 1392-1394, 1988. 

About 150 lipid molecules were present per 1 of enzyme. It was used to esterify 1-phenylethanol with lauric acid in isooctane, giving 95% conversion in 2 h. A lipid-coated lipase has also been used to esterify lauric acid with glycerol in sc carbon dioxide with 90% conversion.98 Catalase with less than 5% of its surface amino groups modified by the nonionic surfactant 9.7 had a higher activity in 1,1,1-trichloroethane than when the enzyme was conjugated with polyethylene glycol.99... 

If an enzyme does not tolerate to be modified by covalent attachment of PEG residues, various lipids, such as simple long-chain fatty acids or amphiphilic compounds can be attached onto its surface by mild adsorption. It has been estimated that about 150 lipid molecules are sufficient to cover an average protein with a lipophilic layer, which makes it soluble in organic solvents [62, 483]. This so-called lipid-coating seems to be applicable to various t5 es of enzymes, such as lipases [484], phospholipases [438], glycosidases [485], and catalase [486]. 

A silicon oligomer was synthesized by the polycondensation of diethoxy-dimethylsilane using lipid-coated lipase from Rhizopus delemar as catalyst in isooctane containing a small amount of water [124]. Polymerization is proposed to be initiated at the OH head group of the coating lipid. 

Y Okahata, Y Fujimoto, K Ijiro. A lipid-coated lipase as an enantioselective ester synthesis catalyst in homogeneous organic solvents. J Org Chem 60 2244—2250, 1995. 

Nishino and coworkers [18] first reported the synthesis of polysiloxanes using lipase D (from Rhizopus delemar), a stable serine esterase, as a catalyst. The authors used a lipid-coated lipase D to catalyze the oligomerization of diethoxydimethylsilane (DEDMS) in isooctane in the presence of 2 wt% of water. The lipid-coated lipase system, in which hydrophilic head groups of the lipids interacted with the enzyme surface and the two long lipophilic alkyl chains extend away from its surface, solubilized the enzyme in... 

Scheme 2.1 A lipid-coated lipase catalyzes the oligomerization of diethoxydimethylsilane (DEDMS) in isooctane containing 2wt% water, where the polymerization occurs at the (-OH) end group of the coated lipid in the enzyme cavity.

Lipid-coated lipase OF Molecular sieves Isooctane... 

Fig. 13.11 Schematic representation of the hollow fiber membrane biorector for the enzymatic hydrolysis of triglycerides. A hydrophilic membrane has been used, coated with lipase on the lipid side [85].

VLDLs, IDLs, and LDLs are closely related to one another. VLDLs formed in the liver (see p. 312) transport triacylglycerols, cholesterol, and phospholipids to other tissues. Like chylomicrons, they are gradually converted into IDL and LDL under the influence of lipoprotein lipase [1]. This process is also stimulated by HDL. Cells that have a demand for cholesterol bind LDL through an interaction between their LDL receptor and ApoB-100, and then take up the complete particle through receptor-mediated endocytosis. This type of transport is mediated by depressions in the membrane ( coated pits"), the interior of which is lined with the protein clathrin. After LDL binding, clathrin promotes invagination of the pits and pinching off of vesicles ( coated vesicles"). The clathrin then dissociates off and is reused. After fusion of the vesicle with ly-sosomes, the LDL particles are broken down (see p. 234), and cholesterol and other lipids are used by the cells. 

In case of lipases, one of the simplest methods to combine an enzyme with an organic solvent is to coat the lipase with a lipid or surfactant layer before lyophilisation. It is estimated that about 150 surfactant molecules are sufficient for encapsulating one lipase molecule. Following this route the surfactant coated lipase forms reverse micelles with a minimum of water concentration. The modified lipases are soluble in most organic solvents, and the reaction rates are increased compared to the suspended hpases due to the interfacial activation [59,60]. 

Fig. 5.6 Experimental setup (top) and schematic representation of a cross section through a hollow fibre (bottom) for the enzymatic conversion of triglycerides into fatty acids [49]. For this purpose a hydrophilic membrane is used, coated with the enzyme (lipase) on the lipid side.

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