Linoleic acid, hydroperoxidation

Yeum, K. J., Y. C. Leekim et al. (1995). Similar metabolites formed from beta-carotene by human gastric-mucosal homogenates, lipoxygenase, or linoleic acid hydroperoxide. Arch. Biochem. Biophys. 321(1) 167-174. 

In contrast to numerous literature data, which indicate that protein oxidation, as a rule, precedes lipid peroxidation, Parinandi et al. [66] found that the modification of proteins in rat myocardial membranes exposed to prooxidants (ferrous ion/ascorbate, cupric ion/tert-butyl-hydroperoxide, linoleic acid hydroperoxide, and soybean lipoxygenase) accompanied lipid peroxidation initiated by these prooxidant systems. 

Figure C4.2.4 (A) SP-HPLC of methyl hydroxyoctadecadienoates obtained from linoleic acid hydroperoxide products. Peak 1, methyl 13-hydroxy-9(Z),11( )-octadecadienoate peak 2, methyl 13-hydroxy-9( ),11(E)-octadecadienoate peak 3, methyl 9-hydroxy-10(E),12(Z)-octadecadi-enoate peak 4, methyl 9-hydroxy-10( ),12( )-octadecadienoate. In this chromatogram, peaks 2 and 4 are more abundant than ordinarily encountered retention times may vary (but not the order of elution) depending on the type of silica HPLC column. (B) CP-HPLC of peak 1 from A. The 13(R)-stereoisomer elutes before the 13(S)-stereoisomer. Elution times may vary. (C) CP-HPLC of peak 3 from A. The 9(S)-stereoisomer elutes before the 9(R)-stereoisomer. Elution times may vary.

The value for e is only approximate here, as the extinction coefficient was based on iodometric PV determinations of an ethanolic solution of linoleic acid hydroperoxide (O Brien, 1969). 

The incubation mixture consisted of 0.1M Tris-HCl pH 6.5, hematin (0.02 mM) and 0.1 mM of DAB, MAB and AB. The reaction was started by the addition of linoleic acid hydroperoxide (0.1 mM) and terminated after 5 minutes at 20°C by extraction with ethyl acetate. The azo dyes and their metabolites were separated and quantified by high performance liquid chromatography. 

TABLE I. METABOLISM OF AMINOAZO DYES BY LINOLEIC ACID HYDROPEROXIDE AND HEME... 

Carcinogenic aminoazo dyes were previously found to increase the latent period of linoleate peroxidation and that DAB was a more effective antioxidant than MAB (13). Furthermore, as autoxidation of the linoleic acid proceeded, N-demethylation of DAB and MAB occurred. Demethylation of DAB also occurred in vitro when DAB is dissolved in cottonseed oil and mixed with ground brown rice (14). Our results clearly indicate that a linoleic acid hydroperoxide-hematin system readily N-demethylates DAB to MAB and MAB to AB. Previously, it was found that in this system, HCHO formation by N-demethylation of DAB was faster than that obtained with MAB (15). Similar results are now reported during the H202 peroxidase catalyzed oxidation of DAB and MAB. Peroxidase and H2O2 have previously been reported to catalyze the N-dealkylation of other arylamines (16, 17). 

Enzyme Assays. Cytochrome P-450 peroxidase activity was determined by the method of O Brien and Rahimthula (27) as modified by Reddy, et al, with cumene hydroperoxide (CHP), linoleic acid hydroperoxide (LHP) and 15-HPETE as substrates and tetramethyl-P-phenylene diamine (TMPD) as electron donor. Prostaglandin H synthase activity was measured as previously described (19). 

Koga S, Nakano M, Uehara K (1991) Mechanism for the generation of superoxide anion and singlet oxygen during heme compound-catalyzed linoleic acid hydroperoxide decomposition. J Biolumin Chemilumin 289 223-229... 

Dix,T. A., and Marnett, L. J. 1985. Conversion of linoleic acid hydroperoxide to hydroxy, keto, epoxyhydroxy, and trihydroxy fatty acids by hematin. J. Biol. Chem., 260, 5351-5357. 

Figure 10-20 Lipoxygenase Catalyzed Formation of Aroma Compounds in Cucumber. Source Reprinted from Biochim. Biophys. Acta., Vol. 441, T. Galliard, D.R. Phillips, and J. Reynolds, The Formation of cw-3-nonenal, mwu-2-nonenal and Hexanol from Linoleic Acid Hydroperoxide Isomers by a Hydroperoxide Cleavage Enzyme System in Cucumber (Cucumis Sativus) Fruits, p. 184, Copyright 1976, with permission from Elsevier Science.

Galliard, T., et al. 1976. The formation of cw-3-none-nal, frarw-2-nonenal and hexanal from linoleic acid hydroperoxide isomers by a hydroperoxide cleavage enzyme system in cucumber (Cucumis sativus) fruits. Biochim. Biophys. Acta 441 181-192. 

HNE[135]. In cultured human fibroblasts [136], exogenous 4-HNE is less toxic than linoleic acid hydroperoxide, but it is much more toxic than MDA[136]. 

An assay which is based on the increase in absorption at 234 nm depends on the fact that the linoleic acid hydroperoxide formed by the action of the enzyme possesses two double bonds in a conjugated system. When arachidonic acid is used as substrate, the maximum is at 238 nm 105). The diene conjugation method, introduced by Theorell et al 91), is sensitive and convenient for kinetic studies, especially when used with a recording spectrophotometer. When preparations of low speciflc activity are used, interference from protein absorption can be a problem. In this case the lipid products can be extracted with hexane. For routine work it is convenient to use Surreys substrate mixture 106). 

Effects of linoleic acid and linoleic acid hydroperoxides on the myofibrils and the solutions of myofibrillar proteins of cod muscle have been proved using the electron microscopy (80). Linoleic acid hydroperoxides were ten times more effective than linoleic acid in reducing the amount of the protein in KCl-extracts from the myofibrils incubated with the acid or its hydroperoxides. Linoleic acid seemed to prevent the dissolution of the myofibril frame work but appeared not to impair the extraction of myosin while hydroperoxides appeared to cause a retention of A-bands (myosin) in the myofibrils. 

Kaneko, T., Honda, S., Nakano, S.I. and Matsuo, M. (1987) Lethal effects of a linoleic acid hydroperoxide and its autoxidation products, unsaturated aliphatic aldehydes on human diploid fibroblasts. Chem.-Biol. Interact. 63 127-137. 

Nerland, D.E., M.M. Iba, and G.J. Mannering (1981). Use of linoleic acid hydroperoxide in the determination of absolute spectra of membrane-bound cytochrome P450. Mol. Pharmacol. 19, 162-167. 

Fukushige, H. C. Wang T.D. Simpson H.W. Gardner D.F. Hildebrand. Purification and identification of linoleic acid hydroperoxides generated by soybean seed lipoxygenases 2 and 3./. Agric. Food Chem. 2005, 53, 5691-5694. 

Peroxides - The destruction of cytochrome P-450 during lipid peroxidation is generally assumed to result from nonspecific degradation of microsomal proteins. Lipid peroxidation indeed causes general protein damage and thus falls outside the scope of this review. Evidence nevertheless exists that lipid peroxides can inactivate cytochrome P-450 enzymes with some specificity (a) lipids extracted from peroxidized microsomes destroy the cytochrome P-450 complement of fresh microsomes, (b) linoleic acid hydroperoxide causes equimolar, concentration-dependent, loss of microsomal cytochrome P-450 and heme, and (c) cytochrome b5 and cytochrome P-450 reductase are not affected except by relatively high concentrations of linoleic acid hydroperoxide. 

Koufimska, L., Pokorny, J., Jaschke, A., and Reblova, Z. 1993. Reactions of linoleic acid hydroperoxide with muscle proteins under storage conditions, in Food Proteins Structure and Functionality, Schwenke, K.D. and Mothes, R., Eds., Weinheim VCH, 236. 

In a system containing multivalent metal ions, such as Cu —Cu or Fe — Fe the hydroperoxides can readily decompose to produce both RO and ROO as the metal ions undergo oxidation-reduction.22 Fukuzaka and Fujii reported that ferrous ions could catalyze the formation of alkoxyl radicals from linoleic acid hydroperoxides during oxidation of food emulsions. 

The alkoxyl radical can also generate a carbonyl to form keto-fatty acids, for example, 13-KODE from linoleic acid hydroperoxide [35,36]. Unlike their hydroxyl connterparts, keto-fatty acids can undergo Michael addition which may account for their ability to activate the transcription factors PPARy and Nrf2/ Keap-1 [37-39]. 

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