Light-dependent modifications in the metabolic responses of squash seedlings

Light-induced modifications in lipoxidase metabolism and chlorophyll formation in the cotyledon of squash (Cucurbita moscata) seedlings were determined. The enzyme activity decreased as light intensity increased, but chlorophyll continued to accumulate long after lipoxidase activity had virtually disappeared. Considering the differences in the levels of irradiance required to manifest the optimal responses, and also from the results obtained with ultraviolet and red, far-red light treatments, any causal relationship between lipoxidase disappearance and chlorophyll synthesis was ruled out.

The observed light-saturation phase in the chlorophyll synthesis, indicated that chlorophyll formation was initially controlled by the phytochrome system. No similar saturation stage for the enzyme responses was observed.

The sensitivity of lipoxidase to prolonged light exposures suggested a strong correlation with the known photoreactions presumed to be controlled by the high energy reactive-phytochrome system. Lipoxidase metabolism is, therefore, suggested as a biochemical index for the photomorphogenic reactions similar to the ones induced by the high energy reaction.

     

Differential inhibitory effects of vitamin E and other antioxidants on prostaglandin synthetase,platelet aggregation and lipoxidase

Prostaglandin biosynthesis from eicosa-8,11,14-trienoic acid in microsomes from the bovine vesicular gland is inhibited by the antioxidants α-naphthol, guaiacol, NDGA and propyl gallate. Prostaglandin biosynthesis in this system is not inhibited by the antioxidants BHT, DL-α-tocopherol and Trolox C. Arachidonic acid induced platelet aggregation is inhibited specifically by α-naphthol, guaiacol, NDGA and propyl gallate. Both arachidonic acid induced platelet aggregation and ADP induced platelet aggregation are inhibited non-specifically by the antioxidants BHT, DL-α-tocopherol and Trolox C. All antioxidants tested in this study inhibit soybean lipoxidase. Thus α-naphthol, NDGA and propyl gallate are non-specific inhibitors of both prostaglandin synthetase and soybean lipoxidase while BHT, DL-α-tocopherol and Trolox C are specific inhibitors of soybean lipoxidase alone.     

Differential inhibitory effects of vitamin E and other antioxidants on prostaglandin synthetase, platelet aggregation and lipoxidase.

Prostaglandin biosynthesis from eicosa-8,11,14-trienoic acid in microsomes from the bovine vesicular gland is inhibited by the antioxidants alpha-naphthol. guaiacol, NDGA and propyl gallate. Prostaglandin biosynthesis in this system is not inhibited by the antioxidants BHT, DL-alpha-tocopherol and Trolox C. Arachidonic acid induced platelet aggregation is inhibited by specifically by alpha-naphthol. guaiacol, NDGA and propyl gallate. Both arachidonic acid induced platelet aggregation and ADP induced platelet aggregation are inhibited non-specifically by the antioxidants BHT, DL-alpha-tocopherol and Trolox C. All antioxidants tested in this study inhibit soybean lipoxidase. Thus alpha-naphthol, NDGA and propyl gallate are non-specific inhibitors of both prostaglandin synthetase and soybean lipoxidase while BHT, DL-alpha-tocopherol and Trolox C are specific inhibitors of soybean lipoxidase alone.     

A spin-reduction assay for lipoxidase.

Spin-label signals are reduced when the nitroxide is present in a lipoxidase reaction mixture. This spin reduction can be used as an assay for enzyme activity in turbid systems where the conventional uv assay cannot be used. Data taken with the spin-reduction assay show that phospholipid preparations containing cholesterol are more resistant to oxidation by lipoxidase than are cholesterol-free preparations.     

Inactivation of slow reacting substance of anaphylaxis (SRS-A) by lipoxidase.

Lipoxidase (E.C.1.13.1.13) inactivates rat SRS-A. The inactivation is time, temperature, and concentration-dependent. Linoleic acid and eicosatetraynoic acid inhibit the enzymatic deactivation of the mediator. It is concluded that SRS-A is a genuine substrate for lipoxidase and contains a cis, cis-1, 4-pentadiene structure. It is suggested that lipoxidase could play a major role in tissue removal of the mediator during hypersensitivity reactions.     

Inactivation of slow reacting substance of anaphylaxis (SRS-A) by lipoxidase

Lipoxidase (E.C.1.13.1.13) inactivates rat SRS-A. The inactivation is time, temperature, and concentration-dependant. Linoleic acid and eicosatetraynoic acid inhibit the enzymatic deactivation of the mediator. It is concluded that SRS-A is a genuine substrate for lipoxidase and contains a cis, cis-1, 4-pentadiene structure. It is suggested that lipoxidase could play a major role in tissue removal of the mediator during hypersensitivity reactions.     

Uptake and metabolism of vitamins e and k by pea stem sections

The uptake of α-tocopherol and vitamin K₁ by pea stem sections is described. Vitamin K₁ appears to be stable within the plant tissue and is found distributed in all particulate cell fractions following uptake. Only a small proportion of the tocopherol taken up is recoverable and the majority of the compound appears to undergo catabolism.

The oxidation of tocopherols by a cell-free system is described. This system requires oxygen and appears to involve enzyme activity but does not appear to be linked with the action of lipoxidase.

     

Effect of N-tris (Hydroxymethyl) Methylglycine and N-2-Hydroxyethyl-piperazine-N'-2-Ethanesulfonic Acid Buffers on Linolenic Acid as a Substrate for Flaxseed Lipoxidase

The delay in, or loss of, flaxseed lipoxidase activity in N-tris (hydroxymethyl) methylglycine and N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid buffers with linolenic acid as a substrate appears due to an alteration of the lipid micelle. Flaxseed lipoxidase activity is dependent on the ionic strength of the assay solution. These effects are not observed with linoleic acid as substrate. The influence of these 2 buffers on linolenic acid micelles may have a direct bearing on recent reports of chloroplast structure and activity in these buffers.     

Action and interaction of red and far-red radiation on lipoxidase metabolism of squash seedlings

Lipoxidase, in the cotyledons of squash (Cucurbita moscata) seedlings grown in the dark, reached its peak activity on the fifth day and then declined to its lowest activity on the eighth day. Under continuous irradiation, the rate of enzyme disappearance was accelerated by red (655 mμ) and was retarded by far-red (735 mμ) radiation. Acceleration of enzyme disappearance caused by red light was reversed repeatedly by far-red light in seedlings that received an initial exposure to red radiation. These responses were independent of the duration of irradiation at each of the alternating wavebands. No change was observed when the white light was administered either 24 hours before or 24 hours after the red, far-red treatment.

The lipoxidase system of the seedlings given an initial exposure to far-red radiation also responded reversibly to alternating far-red, red extended exposures, but it failed to respond reversibly when short exposures were employed. Similarly, no change occurred in these seedlings when either pre- or post-treatment with the white light was applied.

These results demonstrate that the capacity of lipoxidase to act reversibly depends primarily on the duration of exposure and on the kind of light (red or far-red) to which the seedlings were exposed initially. In spite of these variations, lipoxidase metabolism can be considered an additional biochemical manifestation of red, far-red reaction that operates in the photomorphogenesis of plants.

     

无腥味大豆种质创新与利用

大豆是植物油和植物蛋白的主要来源,但大豆蛋白中含有3种结构不同的脂肪氧化酶同功酶,是产生豆腥味的根源,使大豆利用及加工受到限制。从1994年开始我们进行大豆脂氧酶缺失基因的转育与种质创新研究,目前获得了一批综合农艺性状优良的低腥味材料,其中绥无腥豆1号已于2002年3月通过黑龙江省农作物品种审定委员会审定,并开始应用于生产和加工领域。     

Linoleic acid hydroperoxide favours hypochlorite- and myeloperoxidase-induced lipid peroxidation

Liposomes composed of soybean phosphatidylcholine were peroxidized using the reagent sodium hypochlorite or the myeloperoxidase-hydrogen peroxide-Cl^- system. Linoleic acid hydroperoxide previously prepared from linoleic acid by means of lipoxidase was incorporated into liposomes. The yield of thiobarbituric acid reactive substances (TBARS) continuously increased with higher amounts of hydroperoxide groups after the initiation of lipid peroxidation by hypochlorous acid producing systems. The accumulation of TBARS was inhibited by scavengers of free radicals such as butylated hydroxytoluene and by the scavengers of hypochlorous acid, taurine and methionine. Lipid peroxidation was also prevented by sodium azide or chloride free medium in the myeloperoxidase-hydrogen peroxide-Cl^- system. Here we show for the first time that the reaction of hypochlorous acid with a biologically relevant hydroperoxide yields free radicals able to cause further oxidation of lipid molecules.     

Metabolism of chlorophyll in higher plants IV. Relationship between fatty acid oxidation and chlorophyll bleaching in plant extracts

Tissue extracts of various plants actively bleached chlorophyllin the presence of linoleic or linolenic acid. The activityof lipoxidase (linoleate : oxygen oxidoreductase, E.C. 1.13.1.13 [EC] )was necessary for this process, but our experiements providedno evidence for the participation of hydroperoxide isomerase,as has been suggested by other authors. (Received August 3, 1973; )     

Formation of 2-hexenal from linolenic acid by macerated Ginkgo leaves

The content of linolenic acid and its fat-soluble derivatives in Ginkgo leaves has been determined. By utilization of uniformly ¹⁴C-labelled linolenic acid it has been shown that the linolenic acid in Ginkgo leaves is converted into 2-hexenal when the leaves are macerated in the presence of air. The conversion of linolenic acid to 2-hexenal under the conditions of temperature and pH existing in the Ginkgo leaf requires the presence in the leaves of an enzyme or other catalyst. This is not lipoxidase but is a hexane-insoluble, water-soluble substance. A preparation of this substance strongly catalyzes the absorption of oxygen by linolenic acid in water at 20°.     

Der Einfluss von 4-Phenäthylpyridin auf den Fettstoffwechsel bei keimendenSinapis alba L.-Pflanzen

Kind of substrate utilized by the respiration of mustard seedlings (Sinapis alba L.) was determined on the basis of found RQ values of control plants. This led to the study of the effect of 4-phenethylpyridine on relationships between lipase, lipoxidase, glycerolkinase and O₂ consumption: Enzyme activities and O₂ consumption rose from the second to the fifth day. According to these results, 4-phenethylpyridine increases degradation of storage fats in the beginning phase of fat catabolism, bringing about advantageous conditions for their metabolic utilization in plant, like in the case of saccharide metabolism.     

Variation in Polyunsaturates of Special Margarines

Label claims of special margarines offer little information about constituent fatty acids. Nine brands were analyzed with lipoxidase for the cis-methylene-interrupted polyunsaturated fatty acids which are present in unhydrogenated vegetable oils. Although four of these products were advertised as being made from corn oil or containing corn oil, they differed greatly in fatty acid composition. The claim of “polyunsaturates” did not identify those margarines highest in the cis-methylene-interrupted fatty acids. It is noted that regulations are being proposed to set a minimum level for these poly-unsaturated fatty acids in special margarines.     

The inheritance of lipoxidase activity and pigment content in durum wheat

Summary Analysis of a 10-parent diallel of durum wheat (Triticum turgidum L. var. durum) grown at two diverse locations revealed that for enzyme lipoxidase activity, wheat and predicted macaroni pigment contents, heterosis was environmentally dependent. Both additive and dominance genetic effects were significant for each of these quality traits studied, but in one location, the additive genetic effect was consistently more pronounced than the dominance genetic effect, while the reverse was the case in the other location. There was no evidence of epistatic gene effect for any of the three characters in either location.Contribution No. 333.     

Short-term alteration of MAO activity after translocation of calcium in human blood platelets

Incubation of washed human platelets with 5 μM of Ionophore A 23187 leads within 10 min. up to a 100% activation, whereas 50 μM of A 23187 leads to about a 50% inhibition of MAO activity using p-tyramine, tryptamine and benzylamine as substrates. Increase of MAO activity is followed by the calcium dependent activation of cellular phospholipases, the release of arachidonic acid and their subsequent peroxidation into lipoperoxides, prostaglandins and thromboxanes. Inhibition of phospholipase A₂ or lipoxidase and cyclo-oxygenase prevented activation but not inhibition induced by 50 μM of A 23187. The findings indicate that interactions of Ca²⁺ regulated cellular events can lead to short-term activation or inhibition of mitochondrial MAO activity.     

Biosynthesis of ethylene. Enzymes involved in its formation from methional

1. Two enzymes were shown to be necessary for the production of ethylene from methional; they were separated from extracts of cauliflower florets by fractionation on Sephadex and other methods. 2. The first enzyme, generating hydrogen peroxide, appears to be similar to the fungal glucose oxidase, for like the latter it is highly specific for its substrate d-glucose. 3. The second enzyme, in the presence of cofactors and peroxide generated by the first enzyme, cleaves methional to ethylene. 4. It was also found that hydrogen peroxide in these reactions may be replaced by hydroperoxide generated from linolenic acid by lipoxidase enzymes. 5. Dihydroxyphenols were shown to have a marked inhibitory effect on these reactions and to account for the initial phase of low activity that is always observed in aqueous extracts prepared from the floret tissue.     

Trapping of 2,7-dichlorodibenzo-p-dioxin in aqueous solution by enzymatic reaction of fungal manganese peroxidase in the presence of polyunsaturated fatty acids

In the presence of polyunsaturated fatty acids, including cis-4,7,10,13,16,19-docosahexaenoic acid (DHA), 2,7-dichlorodibenzo-p-dioxin (DCDD) was treated with manganese peroxidase (MnP) from white rot basidiomycete Phanerochaete sordida YK-624. After incubation with MnP, DCDD could not be extracted from the reaction mixture with n-hexane and was trapped in the water layer. DCDD was released by alkalification of the water layer. DCDD was also trapped after treatment with lipoxidase, which produces hydroperoxides from unsaturated lipids. The amounts of thiobarbituric acid-reactive substances produced in the MnP reactions with three highly unsaturated fatty acids were higher than the amounts produced with three fatty acids with a lower degree of unsaturation. These results suggest that a DCDD-trapping compound may be produced by peroxidation of the polyunsaturated fatty acids.     

沙芥种子发育过程中的脱水耐性

以发育过程中经脱水和未脱水处理的沙芥种子为试验材料,测定了其含水量、萌发率和抗氧化酶系统,探讨了沙芥种子脱水耐性与抗氧化系统之间的关系。结果表明：在20～60DAF,沙芥种子含水量逐渐下降,干重逐渐增加;60DAF种子具有萌发能力,萌发率为24％;且脱水可促进沙芥种子的萌发,人工脱水至含水量为12％和5％时,萌发率分别为56％和44％,自然脱水至含水量为12％和5％时,萌发率分别为52％和60％;发育过程中沙芥种子SOD活性逐渐降低,而CAT、POD、LOX活性以及MDA含量均呈上升趋势;在脱水过程中,随着种子含水量的下降SOD活性逐渐降低,CAT和LOX活性逐渐升高,而POD活性呈先降低后升高的变化趋势。脱水后,种子中MDA含量均高于CK。60DAF的沙芥种子已获得脱水耐性。