Hydrolysis of lipids

Lipases are the enzymes for which a number of examples of a promiscuous activity have been reported. Thus, in addition to their original activity comprising hydrolysis of lipids and, generally, catalysis of the hydrolysis or formation of carboxylic esters [107], lipases have been found to catalyze not only the carbon-nitrogen bond hydrolysis/formation (in this case, acting as proteases) but also the carbon-carbon bond-forming reactions. The first example of a lipase-catalyzed Michael addition to 2-(trifluoromethyl)propenoic acid was described as early as in 1986 [108]. Michael addition of secondary amines to acrylonitrile is up to 100-fold faster in the presence of various preparations of the hpase from Candida antariica (CAL-B) than in the absence of a biocatalyst (Scheme 5.20) [109]. 

The lipases demonstrated very high stability in media partially or totally composed of organic solvent. In such media, the lipases catalyze esterification, transesterification, and resolution of enantiomers [19,45,75,97-100]. Nevertheless, several biphasic systems (organic-aqueous) are used for hydrolysis of lipid and fats [7,34,101]. Kinetic studies in biphase media or in inverted micelles demonstrate that the lipase behavior is different... 

Determining the degree of hydrolysis of lipids is particularly interesting when degradation is being studied, since the hydrolysis of the ester bond is one of the main decay paths for triglycerides and wax esters. 

L. D. Sutton, J. S. Stout, D. M. Quinn, Dependence of Transition-State Structure on Acyl Chain Length for Cholesterol Esterase Catalyzed Hydrolysis of Lipid p-Nitrophen-yl Esters ,./. Am. Chem. Soc. 1990, 112, 8398-8403. 

The hydrolysis of lipids rarely occurs in a single homogeneous phase, and the behavior of lipases at membrane-solvent and micelle-solvent interfaces has been discussed in detail by Verger and Jain et aP See Micellar Catalysis... 

Lipases are enzymes that catalyze the in vivo hydrolysis of lipids such as triacylglycerols. Lipases are not used in biological systems for ester synthesis, presumably because the large amounts of water present preclude ester formation due to the law of mass action which favors hydrolysis. A different pathway (using the coenzyme A thioester of a carboxylic acid and the enzyme synthase [Blei and Odian, 2000]) is present in biological systems for ester formation. However, lipases do catalyze the in vitro esterification reaction and have been used to synthesize polyesters. The reaction between alcohols and carboxylic acids occurs in organic solvents where the absence of water favors esterification. However, water is a by-product and must be removed efficiently to maximize conversions and molecular weights. 

In general, a fungal lipase from Phycomyces nites catalyzed the hydrolysis of lipids... 

Lipases are serine hydrolases that catalyse the hydrolysis of lipids to fatty acids and glycerol [2]. In contrast to esterases, they work at the lipid-water interface and show only little activity in aqueous solutions. Studies of the X-ray structures of human lipase [3,4] and Mucor miehei lipase [5,6] revealed a change in conformation at the lipid-water interface, which explains the increase of activity. 

Hydrolysis of Lipids Name the products of mild hydrolysis with dilute NaOH of (a) l-stearoyl-2,3-dipalmitoyl-glycerol (b) l-palmitoyl-2-oleoylphosphatidylcholine. 

It is discussed in Chapter 18, Section F, and in Section 7 of this chapter. Also affecting blood pressure is the potent vasorelaxant atrial natriuretic factor. This 28-residue peptide, which is discussed in Box 22-D, is produced by the cardiac atria and stimulates the excretion of Na+ and of water by the kidneys.184 It also promotes hydrolysis of lipids within human adipocytes.185... 

Lipases (E.C. 3.1.1.3.) catalyze the hydrolysis of lipids at an oil/water interface. In a membrane reactor, the enzymes were immobilized both on the side of the water phase of a hydrophobic membrane as well as on the side of the organic phase of a hydrophilic membrane. In both cases, no other means for stabilization of the emulsion at the membrane were required. The synthesis reaction to n-butyl oleate was achieved with lipase from Mucor miehei, which had been immobilized at the wall of a hollow fiber module. The degree of conversion reached 88%, but the substrate butanol decomposed the membrane before the enzyme was deactivated. 

Lipase (Aspergillus niger var.) Produced as an off white to tan, amorphous powder by controlled fermentation using Aspergillus niger var. Soluble in water (the solution is usually light yellow), but practically insoluble in alcohol, in chloroform, and in ether. Major active principle lipase. Typical application used in the hydrolysis of lipids (e.g., fish oil concentrates and cereal-derived lipids). 

Not all ILs are good solvents for proteins, however. There is the interesting example of lipase. Lipase is soluble in both aqueous and organic solvents, so it can be easily solubilized in ILs. Certain lipases even become dispersed or dissolved in some ILs. Since lipase is a very stable enzyme, it catalyzes the hydrolysis of lipids. Enzymatic activity is reported to be maintained in ILs [1]. There is not much published on the solubilization of biomaterials in ILs. In the present chapter we introduce a procedure to use in solubilizing biomaterials in ILs. First we consider the preparation of the IL, and then the chemical modification of biomaterials suitable for dissolution. We have found this procedure helpful when we tried to use electrochemicaUy active biomaterials in ILs. 

For a number of reasons, a great deal of effort has been directed to the degradation of alkanoic acids acetate, propionate, and butyrate are fermentation products of carbohydrates and are metabolites of the aerobic degradation of alklanes and related compounds, while long-chain acids are produced by the hydrolysis of lipids. Studies on the degradation of alkanoic adds have been carried out using both pure cultures and syntrophic associations that have been discussed in Section 4.5.1. 

Fatty acids commonly occur in lipid extracts, where they exist in both free and esterified forms. Free fatty acids are isolated along with the neutral lipids. The esterified fatty acids can be released via hydrolysis of lipids. Negative-ion FAB and ESI are the most suitable modes of ionization for fatty acids. In combination with CID, a wealth of structmal information has been gathered by using these two modes of ionization for fatty acids and other lipid species. Electron ionization (EI)-MS has also been one of the successful mass spectrometric... 

Partial hydrolysis of lipids occur during digestion under the influence of lipases (Sections 11.2 and 11.3). Lipases present in seeds also promote hydrolysis, so that most extracted lipids contain some free acid and some partial glycerides. This is an undesirable change, since removal of free acid during processing is accompanied by some loss of fat. Lipolysis can be minimized by inactivation of the lipase before extraction. Enzymic deacylation is also the basis of some valuable analytical techniques (Section 6.2.17). 

---