[Characteristics of the aggregative state of the substrate in the reaction of 5-lipoxygenase oxidation of linoleic acid]. / Kharakteristika agregatnogo sostoianiia substrata v reaktsii 5-lipoksigenaznogo okisleniia linolevoikisloty.

5-lipoxygenase (EC 1.13.11.12) oxidizes polyunsaturated fatty acids by molecular oxygen. The enzyme acts in close contact with the cell membranes, which main components are ionic and non-ionic lipids. In order to investigate the kinetic parameters of 5-lipoxygenase reaction in vitro, extremely hydrophobic fatty acid substrate (linoleic acid) should be solubilized in the reaction mixture. We used Lubrol PX ("Sigma" Chem. Co), as a non-ionic detergent consisted of oligoethylene glycol and fatty alcohol. Linoleic acid and Lubrol PX formed mixed micelles thus solubilizing the fatty acid substrate in a buffer with appropriate pH. We have studied the sizes and shapes of mixed micelles Lubrol PX/linoleic acid (aggregates type 1) and Lubrol PX/linoleic acid/SDS (aggregates type 2; SDS was an effective activator of potato tuber 5-lipoxygenase) by means of gel-filtration and laser light scattering techniques. The parameters under investigation were molecular weights, Stocks radii and shapes of the mixed micelles. The average molecular weights and Stocks radii of the mixed micelles type 1 determined by mean of gel-filtration on Sephadex G-200 were 95,142 +/- 5184 Da and 3.45 +/- 0.11 nm, respectively. The same parameters for the mixed micelles type 2 were 73,694 +/- 893 Da and 3.02 +/- 0.02 nm, respectively. The strong similarity in physicochemical parameters for both types of mixed micelles indicated that SDS did not influence the size and shape of mixed micelles of Lubrol PX and linoleic acid. The activatory action of SDS on potato tuber lipoxygenase may be a result of electrostatic effect or direct participation of SDS in enzymatic catalysis. The laser light scattering technique allowed to determine two main fraction of particles in type 1 system with hydrodynamic diameters 2.6 and 5.7 nm and relative contribution to light scattering 13 and 87%, respectively. The particles with d = 5.7 nm were interpreted as the mixed micelles. The particles with d = 2.6 nm were interpreted as isolated molecules of Lubrol PX, linoleic acid and (or) their premicellar aggregates. The data obtained are to be used in creation of reliable physical and mathematical models of 5-lipoxygenase.

Enzyme-catalyzed and enzyme-triggered pathways in dioxygenation of 1-monolinoleoyl-rac-glycerol by potato tuber lipoxygenase.

It was shown for the first time that potato tuber lipoxygenase (ptLOX) catalyzed the aerobic oxidation of 1-monolinoleoyl-rac-glycerol (mLG) in a mixed micellar reaction solution with the non-ionic detergent monododecyl ether of decaoxyethylene glycol. No hydrolysis of mLG occurred during the reaction. The four major reaction products obtained at 23 degrees C were identified as 1-[9-hydroperoxy-10E,12Z-octadecadienoyl]-rac-glycerol (9-(E,Z)HPODE-GE, 41%), 1-[13-hydroperoxy-9Z,11E-octadecadienoyl]-rac-glycerol (13-(Z,E)-HPODE-GE, 17%), and their all-trans isomers ( approximately 21% each). The molar fraction of all-trans isomers depended on the temperature of the reaction solution; it was found that at 0 degrees C their molar fractions were approximately 15.5% each, while 9-(E,Z)HPODE-GE and 13-(Z,E)-HPODE-GE gave 42% and 27%, respectively, of the overall product. A free radical scavenger, 4-hydroxy-TEMPO, dramatically increased the molar fraction of 9-(E,Z)HPODE-GE, yielding 83% at 23 degrees C, at the expense of all other products. Chiral HPLC of 9-(E,Z)HPODE-GE formed in the presence of 4-hydroxy-TEMPO revealed that it was composed of approximately 94% S and approximately 6% (R) isomers. This assures largely a uniform orientation of mLG molecules in the ptLOX active center, with their methyl end most likely deepened into the protein globule. The second major product, 13-(Z,E)-HPODE-GE, which yielded approximately 9% of the total product formed in the presence of 4-hydroxy-TEMPO, was racemic, and so were the all-trans isomers. Therefore, the last three cannot be considered the true products of the enzyme reaction, which is known to be stereospecific. It appears that they were formed as a result of (i) leakage of the pentadienyl radicals from the ptLOX active center and their subsequent non-enzymatic dioxygenation, and/or (ii) leakage of the peroxyl radicals leading to a free radical chain reaction affording all positional, geometrical and stereoisomers of the products. This reaction resembles ptLOX oxidation of another non-ionizable substrate, linoleyl alcohol [I.A. Butovich, S.M. Luk'yanova, C.C. Reddy, Arch. Biochem. Biophys. 378 (2000) 65-77], and differed substantially from oxidation of ionizable linoleic acid. Consequently, formation of large amounts of the non-specific oxidation products might be considered a universal characteristic of ptLOX oxidation of non-ionizable compounds.

Oxidation of linoleyl alcohol by potato tuber lipoxygenase: kinetics and positional, stereo, and geometrical (cis, trans) specificity of the reaction.

The dioxygenation of linoleyl alcohol (LAL) by potato tuber lipoxygenase leads to formation of two positional isomeric products--9- and 13-hydroperoxyoctadecadien-1-ols (Butovich, I. A., Luk'yanova, S. M., and Reddy, C. C. (1998) Biochem. Biophys. Res. Commun. 249, 344-349). In the present study, we examined the stereospecificity and double-bond conformation of primary dioxygenation products of LAL catalyzed by potato lipoxygenase. In contrast to the product profiles of linoleic acid oxidation by potato lipoxygenase, oxidation of LAL led to all possible positional (9- and 13-), stereo, and geometrical (cis,trans and all-trans) isomers in equimolar mixtures at 25 degrees C. The reaction appears to proceed through an enzyme-catalyzed formation of a pentadiene carbon-centered radical followed by resonance stabilization of the radical and molecular oxygen insertion in an enzyme-dependent as well as an enzyme-independent pathway. A strict positional, stereo, and geometrical specificity of the dioxygenation products of LAL oxidation appears to be maintained when the reaction occurs at the active site of the enzyme. However, when the pentadiene carbon-centered radical of LAL is dissociated from the active site of the enzyme, it appears to be nonenzymatically transformed into a mixture of all possible positional and geometrical stereoisomers of primary dioxygenation products. The latter pathway was effectively blocked by the free radical scavenger 4-hydroxy-TEMPO, which substantially reduced the production of all-trans hydroperoxyoctadecadienols. In the presence of the scavenger, 9(S)-hydroperoxy-10E,12Z-octadecadien-1-ol was the predominant LAL oxidation product, representing approximately 80% of the total conjugated dienes, with 13(S)-hydroxy-9Z,11E-octadecadien-1-ol the expected product of reverse orientation of the substrate at the active site, accounting for approximately 10%. A similar pattern in oxidation of LAL was observed when the reactions were carried out at 0 degrees C.

[Inhibitory effect of linoleyl-hydroxamic acid on the oxidation of linoleic acid by 12-lipoxygenase from porcine leukocytes]. / Ingibitornoe vliianie linoleil-gidroksamovoi kisloty na oksilenie linolevoi kilsoty 12-lipoksigenazoi iz leikotsitov svin'i.

Linoleic acid oxidation by 12-lipoxygenase from porcine leukocytes has been studied as affected by linoleyl-hydroxamic acid. Linoleyl-hydroxamic acid has been found to be an effective inhibitor of porcine leucocyte 12-lipoxygenase. Aerobic preincubation of 12-lipoxygenase with 0.1-6 microM of linoleyl-hydroxamic acid led to a time- and dose-dependent inhibition of the enzyme. The inhibitor's concentration able to induce a 50% loss of the enzyme activity with and without 15-min preincubation were 3.5 and 0.65 microM, respectively. Experimental results obeyed a kinetic scheme, which supposed 2 extra substrate molecules bounding with the enzyme-substrate complex in the presence of linoleyl-hydroxamic acid.

[Role of phospholipids in the regulation of activity of porcine leukocyte 12-lipoxygenase]. / Rol' fosfolipidov v reguliatsii aktivnosti 12-lipoksigenazy iz leikotsitov svin'i.

12-Lipoxygenase from porcine leukocytes was partially purified by using of DEAE-Toyopearl chromatography (pH 7.5). Phosphatidylcholine and Phosphatidylinositol in reaction mixtures with mixed micelles Lubrol PX/linoleic acid inhibited the enzyme. The pH-optimum of lipoxygenase reaction in presence of phospholipids shifted into alkaline region. In the absence of phospholipids 3 additional substrate molecules bound with enzyme-substrate complex. In the presence of either phosphatidylcholine of phosphatidylinositol up to 2 substrate molecules bound with enzyme-substrate complex. The phospholipids competed with linoleic acid for one of the enzyme binding centers. A kinetic scheme of 12-lipoxygenase reaction has been proposed: Phosphatidylinositol lowered the values of Ks and Kns of the reaction of linoleic acid oxidation by 12-lipoxygenase, while phosphatidylcholine had opposite effect on these parameters. We suppose that phospholipids can regulate 12-lipoxygenase activity via control of the enzyme affinity to the substrate (polyunsaturated fatty acid).

Oxidation of linoleyl alcohol by potato tuber lipoxygenase: possible mechanism and the role of carboxylic group in substrate binding.

We have studied the aerobic oxidation of linoleyl alcohol (LAL) by potato tuber lipoxygenase in the presence of 0.02% (w/v) non-ionic detergent Lubrol PX (and its analog C12E10) and 0.1 mM sodium dodecyl sulfate to investigate the role of carboxylic group in substrate binding. While the enzyme displayed a comparable affinity toward LA and LAL, the rate of LAL oxidation was approximately one-fourth of that of linoleic acid. The pH-profile of the reaction suggests that the rate of LAL oxidation is controlled by two ionizable groups with pKa values of 5.3 and 7.5, with optimal pH being 6.4+/-0.1. Since LAL is not ionizable at this pH, we conclude that the rate of the reaction is controlled by two ionogenic groups of the enzyme. The primary dioxygenation product(s) of LAL had a maximal absorbance at 233+/-1 nm. The products have been isolated, catalytically hydrogenated with H2 over Pd on carbon, and analyzed by GC-MS. Two major equimolar products were found to be 9- and 13-hydroxystearyl alcohols, indicating that 9- and 13-hydroperoxylinoleyl alcohols are the primary dioxygenation products. Based on these results we propose that the carboxyl group of polyunsaturated fatty acid may not be involved in substrate binding of potato tuber lipoxygenase.

[Effect of lipoxygenase derivatives of linoleic acid on functional activity of neutrophils]. / Vliianie lipoksigenaznykh proizvodnykh linolievoi kisloty na funktsional'nuiu aktivnost' neitrofilov.

The effect of lipoxygenase derivatives of 13-hydroperoxylinoleic acid (13-HPODE) and 13-hydroxylinoleic acid (13-HODE) on zymosan-induced chemiluminescence of rat neutrophils in vitro was evaluated. It was found that both derivatives inhibit functional activity of neutrophils. The extent of inhibition was changed by preincubation of neutrophils with arachidonic or linoleic acid. On the other hand, in experiments with dogs it was shown that the extent of such inhibition considerably increases after ischemia and reperfusion of myocardium. Thus we assume that the ratio of lipoxygenase derivatives of arachidonic and linoleic acid play the regulative role in functional activity of neutrophils. It was concluded, that lipoxygenase derivatives of linoleic acid inhibited the neutrophils functional activity.

[Effect of 1,25-dihydroxyvitamin D3 on 15-lipoxygenase activity]. / Vliianie 1,25-dioksivitamina D3 na aktivnost' 15-lipoksigenazy.

The influence of 1.25-dihydroxyvitamin D3 on soybean 15-lipoxygenase activity was studied in vitro. 1.25-Dihydroxyvitamin D3 inhibited enzymatic activity in relation to its dose, pH and substrate (linoleic acid) concentration; the findings are indicative of a mixed type of inhibition.

12-lipoxygenases and 12(S)-HETE: role in cancer metastasis.

Arachidonic acid metabolites have been implicated in multiple steps of carcinogenesis. Their role in tumor cell metastasis, the ultimate challenge for the treatment of cancer patients, are however not well-documented. Arachidonic acid is primarily metabolized through three pathways, i.e., cyclooxygenase, lipoxygenase, and P450-dependent monooxygenase. In this review we focus our attention on one specific lipoxygenase, i.e., 12-lipoxygenase, and its potential role in modulating the metastatic process. In mammalian cells there exist three types of 12-lipoxygenases which differ in tissue distribution, preferential substrates, and profile of their metabolites. Most of these 12-lipoxygenases have been cloned and sequenced, and the molecular and biochemical determinants responsible for catalysis of specific substrates characterized. Solid tumor cells express 12-lipoxygenase mRNA, possess 12-lipoxygenase protein, and biosynthesize 12(S)-HETE [12(S)-hydroxyeicosatetraenoic acid], as revealed by numerous experimental approaches. The ability of tumor cells to generate 12(S)-HETE is positively correlated to their metastatic potential. A large collection of experimental data suggest that 12(S)-HETE is a crucial intracellular signaling molecule that activates protein kinase C and mediates the biological functions of many growth factors and cytokines such as bFGF, PDGF, EGF, and AMF. 12(S)-HETE plays a pivotal role in multiple steps of the metastatic 'cascade' encompassing tumor cell-vasculature interactions, tumor cell motility, proteolysis, invasion, and angiogenesis. The fact that 12-lipoxygenase is expressed in a wide diversity of tumor cell lines and 12(S)-HETE is a key modulatory molecule in metastasis provides the rationale for targeting these molecules in anti-cancer and anti-metastasis therapeutic protocols.

[A hormonally-active form of vitamin D3--1,25-dihydroxyvitamin D3--an inhibitor of leukocyte lipoxygenase]. / Gormonal'no-aktivnaia forma vitamina D3--1,25-dioksivitamin D3-- ingibitor leikotsitarnoi lipoksigenazy.

The effect of the hormonally active vitamin D3 formulation on the activity of porcine leukocyte lipoxygenase was studied. The rate of enzyme inhibition was vitamin dose-dependent and increased if pH values raised, while the vitamin inhibitory effect was decreased as the content of linoleic acid used as a substrate was increased.

[The mechanisms of the changes in coronary vascular resistance in anaphylactic shock]. / O mekhanizmakh izmenenii koronarnogo sosudistogo soprotivleniia pri anafilakticheskom shoke.

Anaphylactic shock decreased the coronary perfusion pressure, systemic arterial pressure and cardiac output in anesthetised dogs. After combined inhibition of cyclo-oxygenase and lipoxygenase with linoleate-hydroxamic acid, the anaphylactic coronary constriction and morphological cardiac lesions were considerably diminished. Activation of the lipoxygenase pathway seems to play a major role in development of the coronary constriction in anaphylaxis.

The unusual action of (R,S)-2-hydroxy-2-trifluoromethyl-trans-n-octadec-4-enoic acid on 5-lipoxygenase from potato tubers.

We found that (R,S)-2-hydroxy-2-trifluoromethyl-trans-n-octadec-4-enoic acid (HTFOA) is a powerful activator of 5-lipoxygenase from potato tubers. The degree of activation of the enzyme is proportional to the HTFOA concentration and is a maximum at about 0.1 mM independently of initial substrate concentration (25 microM or 0.1 mM). At greater concentrations of HTFOA, enzyme inhibition takes place. Enzyme activation is inversely proportional to the substrate (linoleic acid) concentration. The results may be explained by assuming that a regulatory center exists in the enzyme molecule, which shows affinity to both substances: activator and linoleic acid.

[Activation of 5-lipoxygenase by lipophilic n-alkyl-containing acids--an allosteric process]. / Aktivatsiia 5-lipoksigenazy lipofil'nymi n-alkilsoderzhashchimi kislotami--allostericheskii protsess.

Mechanism of the activation of 5-lipoxygenase (EC 1.13.11.12) has been investigated and shown to have the allosteric character. Limitations of the activator structure are formulated.

[Activity of lipoxygenase incorporated into reversed micelles of aerosol OT in octane]. / Aktivnost' lipoksigenazy, vkliuchennoi v obrashchennye mitselly aérozolia OT v oktane.

Soybean lipoxygenase (EC 1.13.11.12) incorporated into the reversed micelles of aerosol OT in octane has been studied for its catalytic properties. The enzyme is shown to preserve up to 10% activity as compared with the activity in the aqueous solution. In this case Km of lipoxygenase for linoleic acid increases from 10(-5) M to 5 X 10(-4) M. The activity of lipoxygenase is maximal, the aerosol OT concentration being 0.03 M and a degree of reversed micelle hydratation 40. Cationic detergents of the cetyltrimethyl ammonium bromide type are not good to form reversed micelles of lipoxygenase, since they inhibit the latter with IC50 = (4 divided by 6) x 10(-4) M. The lipoxygenase preparations in reversed micelles of aerosol OT in octane may be used to synthesize natural metabolites of polyunsaturated fatty acids, for instance of eicosanoids.

[Potato 5-lipoxygenase. Kinetics of linoleic acid oxidation]. / 5-lipoksigenaza kartofelia. Kinetika okisleniia linolevoi kisloty.

The role of main factors influencing the rate of potato 5-lipoxygenase oxidation of linoleic acid was investigated. It was found that nonionic detergent lubrol PX inhibited the potato lipoxygenase. Optimal pH for the linoleic acid oxidation was 6.3 temperature--45 degrees C and substrate concentration--3 x 10(-4) M (if lubrol PX was 0.02%). It was shown that potato 5-lipoxygenase was allosteric enzyme which possessed positive cooperativity for linoleic acid. The Hill coefficient was calculated (n = 1.40 +/- 0.15) with S0.5 = 75 +/- 10 microM.

[Catalytic properties of extracellular phenol oxidases from the higher basidiomycete Pleurotus ostreatus (Fr.) Kumm]. / Kataliticheskie svoistva vnekletochnykh fenoloksidaz vysshego bazidiomitseta Pleurotus ostreatus (Fr.) Kumm.

Phenol oxidase preparations possessing high stability in the reaction of phenols oxidation are isolated from the culture filtrates of four strains of higher basidiomycete Pleurotus ostreatus (F r.) Kumm. The preparations are able to oxidize mono- and diphenols with different substituents in o-, m- and p-positions to phenol hydroxyls as well as o- and p-phenylene diamines. A change in the orientation of substituents in the substrate molecule is followed by a change in the mechanism of its oxidation. The enzyme activity is determined by the type of substituents in the phenol molecule: electron-withdrawing groups impede and electron-releasing ones facilitate the substrate oxidation. The Hammett equation is shown to be applicable for description of monophenol oxidation. An explanation of high values of positive deviations from it in the case of halogen-substituted phenols is suggested. A conclusion is drawn that Km of enzymes for oxygen determined from the full kinetic curves of O2 uptake with phenol redundancy are kinetic constants depending on the substrate structure.