Lipids lipoxygenase

Genes involved in the uptake and degradation of tocopherols - Genes implicated with lipid uptake and. Mi / °f J - Protein kinase C (PKC) - Cyclooxygenase - 5-Lipoxygenase - Cytokine release (IL-1P)... 

Smith WL, Fitzpatrick FA The eicosanoids Cyclooxygenase, lipoxygenase, and epoxygenase pathways. In Biochemistry of Lipids, Lipoproteins and Membranes. Vance DE, Vance JE (editors). Elsevier, 1996. 

Lodge, J.K., Patel, S.U. and Sadler, P.J. (1993). Aldehydes from metal ion- and lipoxygenase-induced lipid peroxidation detection by H-n.m.r. spectroscopy. Biochem. J. 289, 149-153. 

The biological membranes that surround cells and form the boundaries of intracellular organelles contain polyunsaturated fiitty acids, which are susceptible to oxidation. This reaction is used under controlled conditions by enzymes, such as the lipoxygenases or cyclooxygenases, within cells to produce oxygenated lipids, which can act as mediators of inflammation (Smith and Marnett, 1991 Yamamoto, 1992). Such compounds are characterized by their high potency and specificity in their interaction with cells (Salmon, 1986). While these enzymatic reactions... 

An example of an experiment in which LDL has been treated with 15-lipoxygenase and the oxidation monitored by the formation of conjugated diene is shown in Fig. 2.2. In the absence of transition metal, a rapid increase in absorbance occurs, with no lag phase, which ceases after a period of about 90 min under these conditions. If copper is added to promote LDL oxidation at this point, LDL treated with lipoxygenase oxidizes at a faster rate with a short lag phase when compared to the control. During this procedure there is only a minimal loss of a-tocopherol and so we may ascribe the shortened lag phase to the increase in lipid peroxides brought about by lipoxygenase treatment. A similar result was found when LDL was supplemented with preformed fatty acid hydroperoxides (O Leary eta/., 1992). 

Chamirlitrat, W. and Mason, KP. (1989). Lipid preroxyl radical intermediates in the peroxidation of polyunsaturated fatty acids by lipoxygenase. J. Biol. Chem. 264, 20968—20973. 

Kanner, J., Harel, S. and Granit, R (1992). Nitric oxide, an inhibitor of lipid oxidation by lipoxygenase cyclooxygenase and hemoglobin. Lipids 27, 46—49. 

Sparrow, C.P., Parthasarathy, S. and Steinberg, D. (1988). Enzymatic modification of LDL by purified lipoxygenase plus phospholipase Ai mimics cell mediated oxidative modification. J. Lipid Res. 29, 745-733. 

Mechanisms of lipid peroxidation that have been implicated in atherosclerosis may be pertinent to RA. Cellular lipoxygenase enzymes may promote LDL modification by inserting hydroperoxide groups into unsaturated fetty-acid side chains of the LDL complex (Yla-Herttuala etal., 1990). 15-Lipoxygenase has been implicated as an initiator of LDL oxidation (Cathcart etal., 1991) whilst 5-lipoxygenase does not appear to be involved (Jessup et al., 1991). Products of activated lipoxygenase enzymes within inflammatory synovial fluid surest that this pathway could be activated in RA (Costello etal., 1992). 

Cathcart, M.K., McNally, A.K. and Chisolm, G.M. (1991). Lipoxygenase mediated transformation of human low density lipoprotein to an oxidised and cytotoxic complex. J. Lipid Res. 32, 63-70. 

The lipase-catalyzed fatty acid ester hydrolysis and the lipoxygenation of free polyunsaturated fatty acids are involved in the same lipid degradation pathway. They are respectively the first and second reaction in the lipoxygenase pathway (Fig. 3) [87-91]. The pathway produces volatile products of considerable importance in food technology including Cg[92, 93] or Cg- 94—96 aldehydes and alcohols from polyunsaturated fatty... 

Lipid-lowering agents, 40 (2002) 1 5-Lipoxygenase inhibitors and their antiinflammatory activities, 29 (1992) 1 Literature of medicinal chemistry, 6 (1969) 266... 

In this chapter the generation of free radicals, mainly superoxide and nitric oxide, catalyzed by prooxidant enzymes will be considered. Enzymes are apparently able to produce some other free radicals (for example, HO and N02), although their formation is not always rigorously proved or verified. The reactions of such enzymes as lipoxygenase and cyclooxygenase also proceed by free radical mechanism, but the free radicals formed are consumed in their catalytic cycles and probably not to be released outside. Therefore, these enzymes are considered separately in Chapter 26 dedicated to enzymatic lipid peroxidation. 

Lipid peroxidation may proceed by both enzymatic and nonenzymatic pathways. Enzymatic peroxidation is catalyzed by enzymes such as lipoxygenases and cyclooxygenases (COXs) and is considered in Chapter 26. One of the most important questions in the study of the mechanisms of lipid peroxidation is the characteristic of an initiation stage. Obvious... 

Schnurr et al. [22] showed that rabbit 15-LOX oxidized beef heart submitochondrial particles to form phospholipid-bound hydroperoxy- and keto-polyenoic fatty acids and induced the oxidative modification of membrane proteins. It was also found that the total oxygen uptake significantly exceeded the formation of oxygenated polyenoic acids supposedly due to the formation of hydroxyl radicals by the reaction of ubiquinone with lipid 15-LOX-derived hydroperoxides. However, it is impossible to agree with this proposal because it is known for a long time [23] that quinones cannot catalyze the formation of hydroxyl radicals by the Fenton reaction. Oxidation of intracellular unsaturated acids (for example, linoleic and arachidonic acids) by lipoxygenases can be suppressed by fatty acid binding proteins [24]. 

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. 

Flavor is one of the major characteristics that restricts the use of legume flours and proteins in foods. Processing of soybeans, peas and other legumes often results in a wide variety of volatile compounds that contribute flavor notes, such as grassy, beany and rancid flavors. Many of the objectionable flavors come from oxidative deterioration of the unsaturated lipids. The lipoxygenase-catalyzed conversion of unsaturated fatty acids to hydroperoxides, followed by their degradation to volatile and non-volatile compounds, has been identified as one of the important sources of flavor and aroma components of fruits and vegetables. An enzyme-active system, such as raw pea flour, may have most of the necessary enzymes to produce short chain carbonyl compounds. 

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