Enzymatic lipid peroxidation

Biosynthesis of certain biologically active substances (prostaglandins, thromboxanes, prostacyclins and leukotrienes) in animal tissues occurs with participation of cyclooxygenases and lipoxygenases, enzymic systems of lipid peroxidation. In normal physiological and pathological processes the enzymic lipid peroxidation by microsomal dioxygenases is considerably more active than the nonenzymic one in the same membrane structures. The molecular structure of the products of the enzymic and nonenzymic peroxidation of lipids also differs essentially. An assumption is advanced that cytosol lipoxygenase may be an easily dissociating component of the cyclooxygenase multienzymic complex and its transition from the biomembrane to the cell cytoplasm is accompanied by changes in the enzyme conformation and chemical nature of the products resulted from polyenic lipids oxidation catalyzed by the enzyme.     

Antioxidant effect of anthocyanin on enzymatic and non-enzymatic lipid peroxidation.

In vitro enzymatic and non-enzymatic polyunsaturated fatty acid peroxidation was significantly inhibited in a dose dependent manner by purified anthocyanin, a deep-red colour pigment from carrot cell culture. The kinetics showed that anthocyanin is a non-competitive inhibitor of lipid peroxidation. Anthocyanin has been found to be a potent antioxidant compared to classical antioxidants such as butylated hydroxy anisole (BHA), butylated hydroxy toulene (BHT) and alpha tocopherol. This natural agent, in addition to imparting colour to the food, might prevent autooxidation of lipids as well as lipid peroxidation in biological systems.     

Current development in non-enzymatic lipid peroxidation products,isoprostanoids and isofuranoids,in novel biological samples

Abstract

Isoprostanoids and isofuranoids are lipid mediators that can be formed from omega-3 and omega-6 polyunsaturated fatty acids (PUFAs). F₂-isoprostanes formed from arachidonic acid, especially 15-F_2t-isoprostane, are commonly measured in biological tissues for decades as the biomarker for oxidative stress and diseases. Recently, other forms of isoprostanoids derived from adrenic, eicosapentaenoic, and docosahexaenoic acids namely F₂-dihomo-isoprostanes, F₃-isoprostanes, and F₄-neuroprostanes respectively, and isofuranoids including isofurans, dihomo-isofurans, and neurofurans are reported as oxidative damage markers for different metabolisms. The most widely used samples in measuring lipid peroxidation products include but not limited to the blood and urine; other biological fluids, specialized tissues, and cells can also be determined. In this review, measurement of isoprostanoids and isofuranoids in novel biological samples by gas chromatography (GC)–mass spectrometry (MS), GC–MS/MS, liquid chromatography (LC)–MS, and LC–MS/MS will be discussed.     

Surfactant protein A inhibits the non-enzymatic lipid peroxidation of porcine lung surfactant.

The ability of surfactant protein A (SP-A) to inhibit the ascorbate-Fe(2+) induced lipid peroxidation of polyunsaturated fatty acids found in porcine lung surfactant (surfacen) was assessed by measuring the light emission - chemiluminescence during a 180-min incubation period at 37 degrees C. The light emission (chemiluminescence) was concentration dependent. Changes in the fatty acid composition of surfacen were observed when the lung surfactant was incubated in an ascorbate-Fe(2+) system. The main polyunsaturated fatty acids C18:2 n6 and C20:4 n6 found in the lung surfactant decreased considerably after a 180-min lipid peroxidation process. Native SP-A isolated from pig lungs inhibited oxidation of surfactant long chain polyunsaturated fatty acids, mainly arachidonic acid, in a dose-dependent fashion that was half-maximal (60% inhibition) at a concentration of 2.0 microg/ml and almost complete (73.6% inhibition) at 4.0 microg/ml, as indicated by inhibition of light emission and fatty acid composition analysis. At the highest concentration of lung SP-A used a very good correlation between the protection of the most polyunsaturated fatty acids and inhibition of light emission was observed.     

Enzymatic and non-enzymatic assay of superoxide dismutase.

Superoxide dismutase from breef brain and rat liver was assayed in an enzymatic system, using xanthine oxidase, and a non-enzymatic system, based on aerobic reduction of nitro-blue tetrazolium in presence of phenazine methosulphate. The non-enzymatic assay is rapid and simple and permits simulatneous analysis of many samples. Similar results are found by the two methods of assay of superoxide dismutase.     

Melatonin and N-acetyl serotonin inhibit selectively enzymatic and non-enzymatic lipid peroxidation of rat liver microsomes

Melatonin (N-acetyl-5-methoxytryptamine) and its immediate precursor N-acetyl serotonin in the metabolism of tryptophan are free radical scavengers that have been found to protect against non-enzymatic lipid peroxidation in many experimental models. By contrast, little is known about the antioxidant ability of these indoleamines against NADPH enzymatic lipid peroxidation. The light emission produced by rat-liver microsomes, expressed as total cpm during 180 min of incubation at 37 degrees C, was two-fold greater in the presence of ascorbate (0.4mM) when compared with NADPH (0.2 mM). Maximal peaks of light emission produced by microsomes lipid peroxidized with ascorbic-Fe(2+) or NADPH and expressed as cpm were 354,208 (at 60 min) and 135,800 (at 15 min), respectively. During non-enzymatic lipid peroxidation a decrease of total chemiluminescence (inhibition of lipid peroxidation) was observed when increasing concentrations of melatonin were added to liver microsomes. The protective effect was concentration-dependent. The inhibition observed in light emission was coincident with the protection of the most PUFAs. Preincubation of microsomes with N-acetyl serotonin reduced these changes very dramatically. Thus, in the presence of both antioxidants (0.36, 0.75, 1.5 mM), light emission percent inhibition during non-enzymatic (ascorbate-Fe(2+)) lipid peroxidation of rat liver microsomes was for melatonin: 6.12, 16.20, 34.88 and for N-acetyl serotonin: 85.10, 88.48, 84.4 respectively. The incubation of rat liver microsomes in the presence of NADPH (0.36, 0.75, 1.5 mM) produce a sudden increase of chemiluminescence that gradually increased and reached a maximal value at about 15 min; however, N-acetyl serotonin reduced these changes very efficiently.     

"Enzymatic" lipid peroxidation: reactions of mammalian lipoxygenases

Lipoxygenase is a dioxygenase which incorporates one molecule of oxygen at a certain position of unsaturated fatty acids such as arachidonic and linolenic acids. The enzymatic oxygenation of unsaturated fatty acids is stereospecific concomitant with a stereoselective abstraction of hydrogen atom. Fatty acid cyclooxygenase is an atypical lipoxygenase incorporating two molecules of oxygen, and initiates the biosynthesis of prostaglandins and thromboxanes. Arachidonate 5-lipoxygenase is responsible for the leukotriene synthesis. No such bioactive compound has been found as a metabolite of the 12- and 15-lipoxygenase pathways, and their physiological roles are still unclarified. These enzymes have been purified, and their molecular and catalytic properties have been investigated. Their cDNA clones have been isolated, and their nucleotide sequences have been determined deducing the primary structures of the enzymes.     

Enzymatic and non-enzymatic antioxidants in selected Piper species

Piper species, commonly used in diet and traditional medicine were assessed for their antioxidant potential. Catalase activity was predominated in Piper longum, followed by Piper cubeba, green pepper, Piper brachystachyum and Piper nigrum. P. nigrum was richest in glutathione peroxidase and glucose-6-phosphate dehydrogenase, green pepper was richest in peroxidase and vitamin C while vitamin E was more in P. longum and P. nigrum. P. brachystachyum and P. longum were rich sources of vitamin A. All the Piper species had GSH content of around 1 to 2 nM/g tissue. The antioxidant components of Piper species constitute a very efficient system in scavenging a wide variety of reactive oxygen species. Antioxidant potential of Piper species was further confirmed by their ability to curtail in vitro lipid peroxidation by around 30-50% with concomitant increase in GSH content.     

Enzymatic lipid peroxidation and oxidative metabolism of aminazine in brain microsomal fractions]

NAD (P) H-dependent enzymic systems, both of lipid peroxidation and chlorpromazine oxidative metabolism are shown to be localized in the microsomal fractions from human and rat brain. Hydroxy-derivatives of chlorpromazine (e.g. 7-OH-chlorpromazine) formed in the course of enzymic NADPH-dependent metabolism possess antioxidant activity and inhibit lipid peroxidation in the brain microsomes. The properties of enzymic NAD (P) H-dependent oxigenase systems in the membranes of the microsomal reticulum of the liver and brain are compared.     

The mechanism of NADPH-dependent lipid peroxidation. The propagation of lipid peroxidation.

NADPH-dependent lipid peroxidation occurs in two distinct sequential radical steps. The first step, initiation, is the ADP-perferryl ion-catalyzed formation of low levels of lipid hydroperoxides. The second step, propagation, is the iron-catalyzed breakdown of lipid hydroperoxides formed during initiation generating reactive intermediates and products characteristic of lipid peroxidation. Propagation results in the rapid formation of thiobarbituric acid-reactive material and lipid hydroperoxides. Propagation can be catalyzed by ethylenediamine tetraacetate-chelated ferrous ion, diethylenetriamine pentaacetic acid-chelated ferrous ion, or by ferric cytochrome P-450. However, cytochrome P-450 is destroyed during propagation.     

Nitric oxide and lipid peroxidation.

Nitric oxide can both promote and inhibit lipid peroxidation. By itself, nitric oxide acts as a potent inhibitor of the lipid peroxidation chain reaction by scavenging propagatory lipid peroxyl radicals. In addition, nitric oxide can also inhibit many potential initiators of lipid peroxidation, such as peroxidase enzymes. However, in the presence of superoxide, nitric oxide forms peroxynitrite, a powerful oxidant capable of initiating lipid peroxidation and oxidizing lipid soluble antioxidants. The role of nitric oxide in vascular pathology is discussed.     

Enzymatic and non-enzymatic functional attributes of plant microbiome

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Responses of citrus plants to ozone: leaf biochemistry, antioxidant mechanisms and lipid peroxidation.

The effects of ozone upon 3-year-old trees of Clementina mandarin (Citrus clementina Hort. ex Tan.) cv. Marisol exposed for 12 months to ambient (10 nl l(-1)) and high (30 and 65 nl l(-1)) concentrations in open top chambers (OTCs) were investigated. The data showed that in leaves, ozone reduced total chlorophylls, carotenoid and carbohydrate concentration, and increased 1-aminocyclopropane-1-carboxylic acid (ACC) content and ethylene production. In treated plants, the ascorbate leaf pool was decreased, while lipid peroxidation and solute leakage were significantly higher than in ozone-free controls. The data indicated that ozone triggered protective mechanisms against oxidative stress in citrus.     

高温对黄瓜幼苗膜脂过氧化作用的影响

经高温处理后,黄瓜幼苗ＭＤＡ含量显著增加,随着处理时间延长,ＭＤＡ含量不断增加,这说明幼苗的膜系统受到明显伤害。高温处理后,ＰＯＤ活性增强;其中对高温敏感的自交系Ｑ１０增加量较大,耐高温的自交系Ｔ９７增加较少。而高温处理有前后Ｔ９７的ＰＯＤ活性明显比Ｑ１０高。高温处理ｄ后,ＣＡＴ活性降低。同时ＳＯＤ活性逐渐降低,对高温敏感的自交系Ｑ１０降低低较严重。试验表明,保持较高膜保护酶的活性可以降低高温的危     

Enzymatic and non-enzymatic reduction of nitrite by extracts of Neurospora crassa.

Two activites causing nitrite disappearance are found in extracts of Neurospora; one, inducible by nitrate or nitrite and present only in nitrite-utilizing strains, catalyze the stoichiometric reduction of nitrite to ammonia; the other, present in all strains under all conditions, causes the disappearance of nitrite to something other than ammonia. The latter activity has a molecular weight of about 600 and may contain an oligopeptide, a metal, and an SH group(s). It has no known physiological function.     

Role of antibiotics in lipid peroxidation.

Alterations in the levels of lipid peroxides, superoxide dismutase, catalase, glutathione, free fatty acid and serum ceruloplasmin were studied in rats fed with high fat cholesterol diet administered different antibiotics, viz. ampicillin, tetracycline, streptomycin, chloramphenicol and cephalosporin. The concentrations of lipid peroxides, glutathione, free fatty acid decreased in most of the tissues, except in tetracycline, streptomycin and cephalosporin treated rats. The changes observed in the activities of superoxide dismutase and catalase in the liver and kidney of these antibiotics administered groups also are in accordance with the changes in lipid peroxides. The results show that the tetracycline is hepatotoxic and nephrotoxic, while cephalosporin and streptomycin are nephrotoxic.     

Sclerotial development, melanin production and lipid peroxidation bySclerotium rolfsii

Melanin pigments constituted 13.9% (W/W) of sclerotial walls ofSclerotium rolfsii. The lipid and ash contents in sclerotial walls were twice those in hyphal walls of the fungus. Progress in culture age and maturation of sclerotia were always accompanied by increased levels of lipid peroxidation products and melanin. Lipid peroxidation and melanin formation may thus proceed in parallel during sclerotial biogenesis and maturation. Both these processes are strongly affected by Fe²⁺ and by antioxidant vitamins (ascorbic acid), microelements (selenium) and mercapto compounds (glutathione). Myceliogenic germination and lytic activityvia melanin production can thus be affected by (anti)oxidants that could potentially be used for controlling sclerotia-producing fungi without using traditional toxic fungicides.     

Human spermatozoal motility and lipid peroxidation.

Correlation between human spermatozoal motility and lipid peroxidation is worked out following their suspension in native seminal plasma and in Biggers, Whitten and Whittengham (BWW) medium. Spermatozoa suspended in BWW showed higher motility and lesser degree of lipid peroxidation than those suspended in seminal plasma. Further, higher activities of antioxidant enzymes are recorded in the BWW suspended spermatozoa vis a vis those suspended in native seminal plasma.