PubMed Health⌕ Search

Biomedical subjects

T Schewe

Publications and source records attributed to T Schewe.

At least 55 records · Page 3Linked to original sources
PubMed1991

On the reaction of wheat lipoxygenase with arachidonic acid and its oxygenated derivatives.

Lipoxygenase was purified from wheat kernels by means of ammonium sulfate precipitation, gel chromatography on Sephadex G-200 and anion exchange chromatography on DEAE-Sephadex A-50. Arachidonic acid was mainly converted by the wheat lipoxygenase to 5D-hydroperoxy-6E,8Z,11Z,14Z-eicosatetraenoic acid (5D8-HPETE) with other HPETE isomers including 8-HPETE being minor products. At higher concentrations of lipoxygenase, multiple oxygenation products such as 5,15-dihydroxyeicosatetraenoic acid (5,15-diHETE) and, to a lower extent, 8,15-diHETE and lipoxin isomers were detected after reduction of the hydroperoxy derivatives primarily formed. Similar results were obtained with 5D8- or 15L8-hydroxyeicosatetraenoic acid as substrate. Moreover, evidence was obtained for leukotriene A4 synthase activity of the wheat lipoxygenase.

Arachidonate 5-Lipoxygenase↗
PubMed1991

Actions of gallic esters on the arachidonic acid metabolism of human polymorphonuclear leukocytes.

Gallic esters with a varying chain length of its alcohol moiety produced strong inhibition of the conversion of [1-14C]-arachidonic acid to 5S-hydroxy-6E,8Z,11Z,14Z-eicosatetraenoic acid (5-HETE) by isolated human polymorphonuclear leukocytes. Octyl gallate and decyl gallate were the most powerful inhibitors with a concentration of half-inhibition of about 1 mumol . 1-1. Additionally these compounds caused however at 10 mumol . 1-1 a complete inhibition of the incorporation of arachidonic acid in triacylglycerols and phospholipids which is assumed to be a consequence of the damage to the energy metabolism of the cells. In contrast, the other gallic esters enhance the incorporation of arachidonic acid in the ester lipids in addition to moderate inhibition of the 5-lipoxygenase pathway.

Arachidonic Acid↗
PubMed1991

Lipoxygenase-inhibitory action of antiviral polymeric oxidation products of polyphenols.

Various polymeric oxidation products of polyphenols strongly inhibited the purified lipoxygenase of rabbit reticulocytes, whereas the prostaglandin H synthase of sheep vesicular gland was only weakly inhibited. The oxidized polymeric preparations of caffeic acid, 2,5-dihydroxytoluene and 3,4-dihydroxytoluene were the most potent lipoxygenase inhibitors. Since such preparations are also known to inhibit herpes simplex virus in an early stage of the virus-cell interaction it is proposed that lipoxygenase metabolites are involved in virus-induced changes in the cell metabolism.

Animals↗
PubMed1990

Oxygenation of mitochondrial membranes by the erythroid lipoxygenase. Consequences for membrane properties.

The reticulocyte lipoxygenase is able to oxygenate mitochondrial membranes. The main products formed during this reaction are 15S-hydroperoxy-5Z,8Z,11Z,13E-eicosatetraenoic acid (15-HETE) and 13S-hydroperoxy-9Z,11E-octadecadienoic acid (13-HODE). The oxygenation of mitochondrial membranes is accompanied by an inactivation of enzymes localized in the outer and inner mitochondrial membranes, by a drastic change of the passive electric properties and by a destruction of the iron-sulfur clusters of the outer mitochondrial membrane. The possible mechanism of the processes leading to these functional changes is discussed.

Animals↗
PubMed1990

Formation of oxygenase and hydroperoxidase products by the pure reticulocyte lipoxygenase.

The pure reticulocyte lipoxygenase oxygenates free arachidonic acid to 15S- and 12S-HPETE in a ratio of about 10:1 15S-H(P)ETE or its methyl ester can be further converted by the lipoxygenase via three different types of reactions: (i) oxygenase reaction, (ii) hydroperoxidase reaction and (iii) leukotriene synthase reaction. Here we summarize the products formed from arachidonic acid by the reticulocyte lipoxygenase via these three types of reactions.

Animals↗
PubMed1990

The linoleic acid metabolite 9DS-hydroxy-10,12(E,Z)-octadecadienoic acid is a strong proinflammatory mediator in an experimental wound healing model of the rat.

Locally administered 9Ds-hydroxy-10,12(E,Z)-octadecadienoic acid (9-HODE) caused a drastic inflammatory response in the experimental model of granulation tissue formation of the rat according to RUDAS (Arzneimittelforsch. 10,226-229, 1960). Three days after implantation of the polyvinyl chloride rings the granulation tissue became inhomogeneous with proliferation islets surrounded by edematous regions containing a diminished number of cells. The number of polymorphonuclear leukocytes and of macrophages was greatly enhanced in the whole tissue, whereas the number of lymphocytes was reduced. After seven days the whole granulation tissue was loosened, and its mass was twice as high as in the control animals. The number of fibroblasts per area unit and the hydroxyproline content were diminished. Linoleic acid and 13Ls-hydroxy-9,11(Z,E)-octadecadienoic acid (13-HODE) caused also some changes in the formation of granulation tissue, but in a different manner, in particular, without accumulation of polymorphonuclear leukocytes and macrophages, indicating the specificity of the effect of 9-HODE. The recruitment of leukocytes was not due to a direct chemotactic action of 9-HODE as shown in an agarose diffusion test comparing the effects of 9-HODE and leukotriene B4. The possible biological importance of the proinflammatory effect of 9-HODE is discussed.

Animals↗
PubMed1990

The erythroid arachidonate 15-lipoxygenase in rat reticulocytes.

Rat reticulocytes contain an arachidonate 15-lipoxygenase which attacks submitochondrial particles in an identical way as the corresponding enzyme from rabbit reticulocytes. It shows immunological cross-reactivity with a polyclonal antiserum against the rabbit reticulocyte lipoxygenase. It differs from the rabbit enzyme with respect to some kinetic properties and its isoelectric point.

Animals↗
PubMed1989

Occurrence of free and esterified lipoxygenase products in leaves of Glechoma hederacea L. and other Labiatae.

Leaves of Glechoma hederacea L. and other Labiatae contain (9S,10E,12Z,15Z)-9-hydroxy-10,12,15-octadecatrienoic acid, (10E,12Z,15Z)-9-oxo-10,12,15-octadecatrienoic acid, (9S,10E,12Z)-9-hydroxy-10,12-octadecadienoic acid and (10E,12Z)-9-oxo-10,12-octadecadienoic acid in a ratio of 71/14/12/3 (by mass), predominantly esterified in the membrane ester lipids. The leaves contain the highest level of these products, whereas only small amounts were found in the stalk and the roots. The chemical structures of these compounds were established by ultraviolet and infrared spectroscopy, by co-chromatography with authentic standards on various types of HPLC columns including chiral-phase HPLC and gas chromatography/mass spectrometry. The stereochemical specificity indicates the enzymatic origin of the products, most probably via a lipoxygenase reaction. Freshly harvested specimens of G. hederacea L. contain only small amounts of hydroxy-polyenoic fatty acids. Air-drying causes a strong increase in the content of free and esterified (9S,10E,12Z,15Z)-9-hydroxy-10,12,15-octadecatrienoic acid. Up to 80% of the hydroxy fatty acids of the total lipid extracts were esterified in the cellular lipids. The data presented indicate that lipoxygenase products occur in the cellular ester lipids of G. hederacea L. and other Labiatae. The results are discussed in the light of a possible involvement of the lipoxygenase pathway in the natural senescence of leaves.

Chemical Phenomena↗
PubMed1989

Oxygenation of mitochondrial membranes by the reticulocyte lipoxygenase. Action on monoamine oxidase activities A and B.

Incubation of isolated rat liver mitochondria with the pure rabbit reticulocyte lipoxygenase caused a time-dependent inactivation of the monoamine oxidase activities A and B. Furthermore, a conversion of the monoamine oxidase into a diamine oxidase was observed. The inactivation kinetics for both monoamine oxidase activities A and B showed a biphasic behaviour; a reversible short-term inhibition during the first 5 min of incubation was followed by an irreversible inactivation of the enzyme. The kinetic studies suggest that the slow irreversible inactivation of the monoamine oxidase activities is due to secondary reactions subsequent to the initial attack of the lipoxygenase on the mitochondrial outer membrane. During the interaction of the lipoxygenase with the mitochondria, only about 1.5% of the polyenoic fatty acids present in the mitochondrial membranes were oxygenated. The predominant products formed during the interaction of the lipoxygenase with the mitochondrial membranes are (13S)-hydro(pero)xy-9Z,11E-octadecadienoic acid and (15S)-hydro(pero)xy-5,8,11,13(Z,Z,Z,E)-eicosatetraenoic acid.

Animals↗
PubMed1989

Occurrence of the erythroid cell specific arachidonate 15-lipoxygenase in human reticulocytes.

Human reticulocytes obtained from patients suffering from various haemolytic disorders convert exogenous [1-14C]-arachidonic acid to 15-hydroxy-5,8,11,13(Z,Z,Z,E)-eicosatetraenoic acid (15-HETE). Immunological studies (dot blot, Western blot) indicated that human reticulocytes contain a lipoxygenase which cross-reacts with a polyclonal antiserum against the rabbit reticulocyte lipoxygenase. Northern blotting with a cloned lipoxygenase cDNA probe shows that the specific mRNA is also present. Reaction of the lipoxygenase with submitochondrial particles caused inactivation of respiratory enzymes. The occurrence of an erythroid cell specific lipoxygenase of similar type in reticulocytes of various mammals and man suggests the general role of this enzyme in the maturational degradation of mitochondria.

Anemia↗
PubMed1988

The biological dynamics of lipoxygenase in rabbit red cells in the course of an experimental bleeding anaemia. Unexpected effects of the calcium ionophore A 23187.

The lipoxygenase activity of red cell lysates with linoleic acid as substrate, the concentration of immunologically detectable lipoxygenase protein as well as the metabolization of external [1-14C]arachidonic or -linoleic acid by intact cells were determined during bleeding anaemia and the recovery period of rabbits. All three criteria behaved in a parallel manner. Before bleeding no lipoxygenase was detectable. After the third day of strong bleeding high amounts and activities of lipoxygenase appeared in parallel to the appearance of megaloreticulocytes. As few as about a million of cells were sufficient to detect the utilization of [1-14C]polyenoic fatty acids via the lipoxygenase pathway in intact cells in the absence of ionophore A 23187. After discontinuation of strong bleeding the amount and activity of the lipoxygenase declined gradually but persisted for 2-3 months corresponding to the presumed life-span of red cells. Several types of evidence indicate the identity of the lipoxygenase of red cells during the recovery period with that of reticulocytes during strong bleeding: (1) comparable specific activity, (2) Western blot analysis, (3) identical cellular products from [1-14C]-linoleic and -arachidonic acid which were identified by means of HPLC analysis to be 13 S-hydroxyoctadecadienoic acid (13 S-HODE) and 15 S-hydroxyeicosatetraenoic acid (15 S-HETE), respectively. Use of large amounts of cells during the recovery period (5.10(9) cells) led to an apparent masking of the polyenoic fatty acid added. Haemolysis of the cells or addition of calcium and ionophore A 23187 abolished or reduced this masking. Both masking and influence of haemolysis or ionophore disappeared at sufficiently low concentrations of cells. Under these conditions the rate of the formation of lipoxygenase products in intact cells corresponded to the lipoxygenase activity measured in membrane-free cell lysates. In red cells during the recovery period but not during strong bleeding, calcium and ionophore A 23187 stimulated the secondary conversion of 15 S-HETE to more polar products after arachidonic acid had been exhausted. The implications of the results on the performance and the interpretation of the effects of the calcium ionophore A 23187 on cellular arachidonic acid metabolism are discussed.

Anemia↗
PubMed1988

Antiinflammatory effect of a lipoxygenase inhibitor (FLM 5011) in severe active myocarditis.

FLM 5011 belongs to a group of chemical compounds with isolated lipoxygenase products in human polymorphonuclear leukocytes and alveolar macrophages. FLM 5011 has been shown to be protective against arachidonic acid-induced bronchoconstriction in vitro and in vivo. No severe side-effects were found in extensive tests on acute and subchronic toxicity in animals. In preliminary investigations on patients with severe active myocarditis impressive clinical and histological improvements after administration of FLM 5011 have been obtained, suggesting an antiinflammatory effect of the substance. A follow-up of more than 13 months compared with conventional immunosuppressive therapy indicates potential therapeutic value of this compound on the inflamed myocardium.

Adult↗
PubMed1988

Inhibition of cell migrations by the linoleic acid oxygenation product 9S-hydroxy 10E,12Z octadecadienoic acid (9-HODE).

The linoleic acid metabolite 9S-HODE was prepared by means of tomato fruit lipoxygenase and purified by high-performance liquid chromatography (HPLC) to a high steric purity as judged by chiral-phase HPLC. 9S-HODE caused in the concentration range between 0.01 and 1 microM a strong dose-dependent inhibition of the migration of both cultured porcine aortic endothelial cells and of phytohaemagglutinin-stimulated human mononuclear cells. The effect was not observed with another polyenoic fatty acid metabolite, 15S-hydroperoxy-5Z,8Z,11Z,13E-eicosatetraenoic acid (15-HPETE). The results are discussed in the light of other biological actions of 9-HODE recently described.

Animals↗
PubMed1987

A kinetic model for lipoxygenases based on experimental data with the lipoxygenase of reticulocytes.

A comprehensive kinetic model for lipoxygenase catalysis is proposed which includes the simultaneous occurrence of dioxygenase and hydroperoxidase activities and is based on the assumption of a single binding site for substrate fatty acid and product. The aerobic reaction of purified lipoxygenase from rabbit reticulocytes with 9,12(Z,Z)-octadecadienoic acid (linoleic acid) as substrate was studied. The rate constants and the dissociation constants of this enzyme were calculated for the model from progress curves; the model describes correctly the experimental data. The following kinetic features of the reticulocyte enzyme are assumed to apply generally to lipoxygenases. (a) The enzyme shows autoactivation by its product. (b) The rate-limiting step is the hydrogen abstraction. (c) Both substrate fatty acid and its product are competitive inhibitors of the lipoxygenase. (d) Lowering the oxygen concentration enhances the degree of substrate inhibition, whereas product inhibition is not influenced. (e) If substrate is in excess the oxygen concentration determines the share of dioxygenase and hydroperoxidase activities of the enzyme. As predicted from the model it was found that at low concentrations of oxygen the regio- and stereo-specificities of the dioxygenation are diminished. During the autoactivation phase the steady-state approximation does not hold.

Animals↗
PubMed1987

Analysis of the stereochemistry of lipoxygenase-derived hydroxypolyenoic fatty acids by means of chiral phase high-pressure liquid chromatography.

A chiral phase HPLC method was developed for the simultaneous determination of the positional and optical isomers of the lipoxygenase-derived hydroxypolyenoic fatty acids. With a Bakerbond chiral phase HPLC column (dinitrobenzoyl phenylglycine as chiral phase) the positional and optical isomers of the reduced dioxygenation products (by triphenylphosphine or borohydride) of linoleic acid and arachidonic acid were separated after methylation of the carboxylic groups. No cumbersome chemical derivatization such as conversion to a diastereomer was necessary. As compared with the methods used up till now chiral phase HPLC proved to be simpler and more sensitive. About 10 pmol of hydroxy fatty acids suffice for an analysis. The chiral phase HPLC can be used for the preparative separation of the optical antipodes of the lipoxygenase products. An optical purity of more than 90% can be reached in one preparative run. The method was applied to the determination of the stereochemistry of the dioxygenation products of polyenoic fatty acids formed by the lipoxygenases from soybeans, reticulocytes, pea seeds (isoenzyme I and II), tomato fruits, by the quasilipoxygenase activity of hemoglobin, and by the methylene blue-mediated photooxidation of arachidonic acid.

Animals↗