Hydrolysis reaction fatty acids

Lipase is an enzyme which catalyzes the hydrolysis of fatty acid esters normally in an aqueous environment in living systems. However, hpases are sometimes stable in organic solvents and can be used as catalyst for esterifications and transesterifications. By utihzing such catalytic specificities of lipase, functional aliphatic polyesters have been synthesized by various polymerization modes. Typical reaction types of hpase-catalyzed polymerization leading to polyesters are summarized in Scheme 1. Lipase-catalyzed polymerizations also produced polycarbonates and polyphosphates. 

The natural substrates of lipases are triglycerides and, in an aqueous environment, lipases catalyze their hydrolysis into fatty acids and glycerol. In anhydrous media, lipases can be active in the reverse reaction [19]. In fact, in the acylation step, acids, lactones, (cyclic) carbonates [20, 21], cyclic amides [22, 23], (cyclic) thioesters [24, 25], and cyclic phosphates [26] have been found to act as suitable acyl donors. In the deacylation step, apart from water, lipases also accept alcohols [27], amines [28, 29], and thiols [30] as nucleophiles although the specificity of lipases is lower for amines and thiols than for water and alcohols [31]. 

T6. The Action of Phospholipases The venom of the Eastern diamondback rattler and the Indian cobra contains phospholipase A2, which catalyzes the hydrolysis of fatty acids at the C-2 position of glycerophospholipids. The phospholipid breakdown product of this reaction is lysolecithin (lecithin is phosphatidylcholine). At high concentrations, this and other lysophospholipids act as detergents, dissolving the membranes of erythrocytes and lysing the cells. Extensive hemolysis may be life-threatening. 

Hydrolytic enzymes such as lipases catalyze hydrolysis of esters in aqueous media, but when used in non-aqueous media such as organic solvents, ionic liquids and supercritical fluids, they catalyze reverse reactions the synthesis of esters. For example, lipases in natural environment catalyze the hydrolysis of fatty acid esters as shown in Figure 6(a). However, when they are used in organic solvents, they catalyze the esterification reaction (Figure 6(b)). 

In titrimetric methods, LPS catalyzes the hydrolysis of fatty acids from an emulsion of olive oil or oleic acid. The fatty acids liberated are titrated with dilute allcali. Kinetic versions use an automated potentiometric titrator (an instrument commonly referred to as a "pH-stat ). The amount of aUcah used is recorded as a function of time and serves as a measure of fatty acid produced during the reaction. This method has been proposed as reference measurement procedure, useful in the evaluation of new LPS methods. ... 

In tlie turbidimetric method, LPS catalyzes the hydrolysis of fatty acids from an emulsion of oleic acid with a simultaneous decrease in the turbidity of the reaction mixture. Absorbance at 340 nm is read and the AA/min is taken as a measure of LPS activity. This method requires the use of a LPS cahbrator. Turbidities have occasionally been observed to increase rather than to decrease during the reaction period. Such increases have frequently been observed in specimens containing rheumatoid factor. The method linearity ( 3 times the upper reference limit) is hmited, with many clinical samples needhig to be diluted. The upper reference limit at 30°C was reported to be 150U/L. 

For this reason, ester hydrolysis is usually carried out in basic solutions. Note that NaOH does not act as a catalyst rather, it is consumed by the reaction. The term saponification (meaning soapmaking) was originally used to describe the alkaline hydrolysis of fatty acid esters to yield soap molecules (sodium stearate) ... 

Although, normally, in the aqueous environment associated with a living system, Hpase wiU catalyze the hydrolysis of fatty acid esters, certain isolated lipases have been found to be stable in organic solvents and capable of serving as a catalyst for the reverse reaction [1, 2]. Hence, by employing a lipase-mediated catalysis of esterifications and transesterifications in an organic medium, functional aliphatic polyesters have been created with a variety of polymerization modes (Scheme 23.7). 

Based on the specific reaction that they catalyze, enzymes have been classified into six groups, three of which have been reported to catalyze or induce polymerization in vitro, namely oxidoreductases, transferases and hydrolases. The latter class includes hpases, the natural role of which is the hydrolysis of fatty acid esters at the cell s water-Upid interface. In organic media, hpases can efficiently catalyze ester bond formation, and so have been used extensively in investigations of the in vitro synthesis of polyester by polycondensation or ring-opening polymerization (ROP), without the need for any cocatalyst. One enzyme that deserves special attention when discussing enzymatic ROP is Candida antarctica Lipase B (CALB). 

Although extraction of lipids from membranes can be induced in atomic force apparatus (Leckband et al., 1994) and biomembrane force probe (Evans et al., 1991) experiments, spontaneous dissociation of a lipid from a membrane occurs very rarely because it involves an energy barrier of about 20 kcal/mol (Cevc and Marsh, 1987). However, lipids are known to be extracted from membranes by various enzymes. One such enzyme is phospholipase A2 (PLA2), which complexes with membrane surfaces, destabilizes a phospholipid, extracts it from the membrane, and catalyzes the hydrolysis reaction of the srir2-acyl chain of the lipid, producing lysophospholipids and fatty acids (Slotboom et al., 1982 Dennis, 1983 Jain et al., 1995). SMD simulations were employed to investigate the extraction of a lipid molecule from a DLPE monolayer by human synovial PLA2 (see Eig. 6b), and to compare this process to the extraction of a lipid from a lipid monolayer into the aqueous phase (Stepaniants et al., 1997). 

Fatty acids are susceptible to oxidative attack and cleavage of the fatty acid chain. As oxidation proceeds, the shorter-chain fatty acids break off and produce progressively higher levels of malodorous material. This condition is known as rancidity. Another source of rancidity in fatty foods is the enzymatic hydrolysis of the fatty acid from the glycerol. The effect of this reaction on nutritional aspects of foods is poorly understood andhttie research has been done in the area. 

Manufacture of Fatty Acids and Derivatives. Splitting of fats to produce fatty acids and glycerol (a valuable coproduct) has been practiced since before the 1890s. In early processes, concentrated alkaU reacted with fats to produce soaps followed by acidulation to produce the fatty acids. Acid-catalyzed hydrolysis, mostly with sulfuric and sulfonic acids, was also practiced. Pressurized equipment was introduced to accelerate the rate of the process, and finally continuous processes were developed to maximize completeness of the reaction (105). Lipolytic enzymes maybe utilized to spHt... 

In general, the presence of fatty acid groups in the phosphoHpid molecule permits reactions such as saponification, hydrolysis, hydrogenation, halogenation, sulfonation, phosphorylation, elaidinization, and ozonization (6). 

Saponification can proceed direcdy as a one-step reaction as shown above, or it can be achieved indirectly by a two-step reaction where the intermediate step generates fatty acids through simple hydrolysis of the fats and oils and the finishing step forms soap through the neutralization of the fatty acid with caustic soda. There are practical considerations which must be addressed when performing this reaction on a commercial scale. 

Enzyme—Heat—Enzyme Process. The enzyme—heat—enzyme (EHE) process was the first industrial enzymatic Hquefaction procedure developed and utilizes a B. subtilis, also referred to as B. amjloliquefaciens, a-amylase for hydrolysis. The enzyme can be used at temperatures up to about 90°C before a significant loss in activity occurs. After an initial hydrolysis step a high temperature heat treatment step is needed to solubilize residual starch present as a fatty acid/amylose complex. The heat treatment inactivates the a-amylase, thus a second addition of enzyme is required to complete the reaction. 

Hydrolysis using aqueous alkaH has been found to remove ash material including pyrite. A small pilot plant for studying this process was built at the BatteUe Memorial Institute in Columbus, Ohio (74) and subsequentiy discontinued. Other studies have produced a variety of gases and organic compounds such as phenols, nitrogen bases, Hquid hydrocarbons, and fatty acids totaling as much as 13 wt % of the coal. The products indicate that oxidation and other reactions as weU as hydrolysis take place. 

Hydrolysis by Steam. High pressure steam, 4.5—5.0 MPa (650—725 psi), at 250°C in the absence of a catalyst hydroly2es oils and fats to the fatty acids and glycerol (20). The reaction is commonly carried out continuously in a countercurrent method. The glycerol produced during the reaction is continuously extracted from the equiUbrium mixture with water. A yield of 98% can be achieved. Currentiy, the preferred method to produce soaps is steam hydrolysis of fats followed by alkaU neutrali2ation of the fatty acids. 

FIGURE 24.7 The acyl-CoA synthetase reaction activates fatty acids for /3-oxidation. The reaction is driven by hydrolysis of ATP to AMP and pyrophosphate and by the subsequent hydrolysis of pyrophosphate. 

The metabolic breakdown of triacylglycerols begins with their hydrolysis to yield glycerol plus fatty acids. The reaction is catalyzed by a lipase, whose mechanism of action is shown in Figure 29.2. The active site of the enzyme contains a catalytic triad of aspartic acid, histidine, and serine residues, which act cooperatively to provide the necessary acid and base catalysis for the individual steps. Hydrolysis is accomplished by two sequential nucleophilic acyl substitution reactions, one that covalently binds an acyl group to the side chain -OH of a serine residue on the enzyme and a second that frees the fatty acid from the enzyme. 

The fatty acids released on triacylglycerol hydrolysis are transported to mitochondria and degraded to acetyl CoA, while the glycerol is carried to the liver for further metabolism. In the liver, glycerol is first phosphorylated by reaction with ATP. Oxidation by NAD+ then yields dihydroxyacetone phosphate (DHAP), which enters the carbohydrate metabolic pathway. We ll discuss this carbohydrate pathway in more detail in Section 29.5. 

Discussion. For oils and fats, which are esters of long-chain fatty acids, the saponification value (or number) is defined as the number of milligrams of potassium hydroxide which will neutralise the free fatty acids obtained from the hydrolysis of 1 g of the oil or fat. This means that the saponification number is inversely proportional to the relative molecular masses of the fatty acids obtained from the esters. A typical reaction from the hydrolysis of a glyceride is ... 

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