Hydrolysis complex lipids

SIMP LB LIPIDS (one or two products after hydrolysis) COMPLEX LIPIDS (three or more products after hydrolysis) ... 

Most authors have classihed lipids into two major groups such as neutral and polar lipids, whereas some dehne them as simple and complex lipids. Simple lipids yield a maximum of two primary products per mole after hydrolysis, whereas complex lipids yield three or more primary products. 

Complex lipids Lipids whose hydrolysis produces several other biomolecules, such as fatty acids, simple sugars, glycerol, sphingosine, etc. 

There are basically two mechanisms to convert the fatty acids in a complex lipid to fatty acid methyl esters (FAMEs) methylation following hydrolysis of the fatty acids from the complex lipids, or direct transesterification. The first mechanism involves saponification (alkaline hydrolysis) in which the ester bond is cleaved between the fatty acid and the glycerol moiety (e.g., triacylglycerols and phospholipids) under heat and in the presence of an alkali (usually sodium hydroxide), followed by methylation performed in the presence of an acidic catalyst in methanol. Direct transesterification is usually a one-step reaction involving alkaline or acidic catalysts. 

IR spectroscopy can also be used to monitor the progress of biological reactions. For example, the hydrolysis of complex lipids (esters of glycerol) causes a characteristic decrease in intensity of the ester carbonyl absorption at 1735 cm-1, with a corresponding appearance of a carboxylic acid absorption near 1710 cm-1. 

Oxidative phosphorylation is central to the metabolism of all higher organisms, because the free energy of hydrolysis of the ATP so generated is used in the synthesis of, inter alia, nucleic acids (Chaps. 7 and 16), proteins (Chaps. 4,9, and 17), and complex lipids (Chap. 6), as well as in processes as diverse as muscle contraction (Chap. 5) and the transmission of nerve impulses. 

The number of products after hydrolysis simple lipids or complex lipids) (Table 1), Fig. (1). 

COMPLEX LIPIDS (three or more products after hydrolysis)... 

The chemistry of complex lipids is dominated by regioselective hydrolysis reactions of (1) the glyceryl fatty acid esters and (2) phosphate diesters. Both types of reactions are routinely performed with the corresponding esterases. A large variety of lipid active transferase enzymes is also commercially available. Phospholipases Aj, A, C, and D, for example, split any of the four ester bonds of a phospholipid regioselectively. The product without a fatty acid side chain at C2 of glycerol is called a lysophospholipid. Lecithin-cholesterol-acyltransferase transfers the fatty acid at C2, often linoleic acid, to the OH group at C3 of cho-... 

Other oxidation products include epoxides that can arise from hydroperoxide rearranganent [25-27], but are also formed by enzymic processes [28,29], Products of lipid oxidation may be quantified after formation from simple lipids, for example, oxidation of cholesterol or PUFA. These lipids may be components of more complex lipids like cholesteryl esters [30] or PUFA-containing phospholipids [31]. An analysis of the oxidized products can be performed on the intact lipid or after the individual Upid components are separated by hydrolysis. 

In many instances, oxidized products are considerably more stable when formed in complex lipids, like phospholipids or cholesteryl esters, and alkaline hydrolysis is required to release the oxidized lipid for analysis. Separation and quantitation of mono-hydroxyicosanoids by HPLC has been regularly used for the last 30 years. The procedures have become routine and there are now published procedures for automating the analysis [60]. A recent review by Yin et al. [36] describes in detail how to quantify both mono-hydroxyeicosatetraenoates and F2-isoprostanes. Similar procedures can be used to separate and identify products derived from (5Z,8Z,llZ,14Z,17Z)-eicosa-5,8,11,14,17-pentenoic acid, (7Z,10Z,13Z,16Z,19Z)-docosa-7,10,13,16,19-pentaenoic acid, and (4Z,7Z,10Z,13Z,16Z,19Z)-docosa-4,7,10,13,16,19-hexaenoic acid. 

TLC has found its principal application in the fractionation of complex lipids into compoxmd classes (see p. 374). Further subdivision of these lipid classes is not as a rule carried out, although good methods are available (see p. 394) on the contrary, an aliquot is hydrolysed and the composition of the fatty acids and other components determined gas chromatographically. Even the identification of a pure compound, e. g., a triglyceride, requires qualitative and quantitative analysis of both the lipophilic and hydrophilic hydrolysis products (fatty acids and... 

Complex lipids readily undergo hydrolysis, while simple lipids do not undergo hydrolysis. 

In the biosphere, triesters of orthophosphoric acid are unknown, however, this does not exclude the possibility that this binding may be present in certain macromolecules. The diesters of orthophosphoric acid which exist in the biosphere are often mixed esters. Acid or alkaline hydrolysis slowly transforms them into monoesters. Most of the complex lipides are diesters and vitamin also falls into this category. The mono-phosphoric esters of alcohols form a very important biochemical group. The two free acid groups are more strongly acidic than when they were... 

Based on the features of chromatographic separation, lipids are classified into simple and complex molecules [2]. Simple lipids are those that yield mostly two types of primary products per molecule upon hydrolysis (e.g., fatty acids and their derivatives, MAG) complex lipids yield three or more primary hydrolysis products per molecule (e.g., PC, TAG, DAG). These hydrolysis products include fatty acids, phosphoric acid, organic bases, carbohydrates, glycerol, and many more components. 

Complex lipides resemble the fats physically, and yield aliphatic acids on hydrolysis. They differ chemically from the simple lipides in containing phosphoric acid or galactose in the molecule, usually associated with a basic nitrogen compound. The presence of nitrogen is indicated in the alternative name Lipine. 

Absorption of Lipides.—In order to be absorbed, simple and complex lipides must first undergo hydrolysis to aliphatic acids. These acids then combine with the bile salts to form water-soluble, diffusible complexes, which pass into the intestinal mucosa, where they interact with glycerophosphoric acid to regenerate the neutral fat, and thus enter the lymphatics. Hence, three factors are concerned in fat absorption (i.) the enzyme lipase and its activators (ii.) the bile salts, which act as carriers (iii.) the phosphorylation mechanism in the mucosa, which in turn, requires vitamin Bj (p. 257) and the hormone of the adrenal cortex (p. 415), as demonstrated by Verzar. This elaborate mechanism endows the organism with considerable power of discrimination in the absorption of lipides and lipoids, as shown by the preferential absorption of carotene. 

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). 

A subfamily of Rho proteins, the Rnd family of small GTPases, are always GTP-bound and seem to be regulated by expression and localization rather than by nucleotide exchange and hydrolysis. Many Rho GTPase effectors have been identified, including protein and lipid kinases, phospholipase D and numerous adaptor proteins. One of the best characterized effector of RhoA is Rho kinase, which phosphorylates and inactivates myosin phosphatase thereby RhoA causes activation of actomyosin complexes. Rho proteins are preferred targets of bacterial protein toxins ( bacterial toxins). 

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