大豆脂肪氧化酶催化油酸氧化反应动力学研究

用（NH4）2SO4三次盐析法从大豆中提取脂肪氧化酶；用测氧仪测定和跟踪脂肪氧化酶催化油酸氧化反应的反应过程。实验表明，脂肪氧化酶催化油酸氧化反应是按Michaelis机理进行。其最佳反应条件是：pH＝9．0；反应温度t＝30℃。反应活化能Ea＝74．95kJ·mol－1；米氏常数KM＝2．97×10－3mol·L－1。本文还测出了多种抑制剂对脂肪氧化酶的抑制效果。在应用方面提出了用抑制剂除去豆腥味的新方法。     

Enzymes and receptors in the leukotriene cascade

Leukotrienes are a family of paracrine hormones derived from the oxidative metabolism of arachidonic acid. These lipid mediators are recognized as important signal molecules in a variety of inflammatory and allergic conditions affecting the skin, joints, gastrointestinal and respiratory systems, in particular asthma. Such conditions are typified by local pain, tissue edema, hyperemia and functional losses. In the tissues, immunocompetent cells accumulate at the site of injury which contribute to tissue damage and perpetuation of the disease process. Leukotrienes can elicit most, if not all, of these signs and symptoms. Thus, leukotriene B₄ is one of the most powerful chemotactic agents known to date and participates in the recruitment of leukocytes. The cysteinyl leukotrienes, on the other hand, contract smooth muscles, particularly in the peripheral airways and microcirculation. Recently, drugs which block the formation and action of leukotrienes have been introduced as novel antiasthmatic medications. This chapter reviews the biochemistry, molecular biology and cell biology of the key enzymes and cognate receptors in the leukotriene cascade.     

温度对叶片延迟发光的影响

以绿宝石喜林芋叶片为材料研究了不同温度对叶片延迟发光和超氧物歧化酶(SOD)、脂氧合酶(LOX)活性的影响.结果表明:随温度的升高,延迟发光的衰减系数先增加后减小,在15 ℃时有一最大值;延迟发光的最大强度也会随温度的不同而发生改变,当温度达到50 ℃时,叶片基本上不再具有延迟发光的特性;SOD,LOX活性与延迟发光之间存在极为密切的关系.     

Evidence that the establishment of pregnancy requires activation of lipoxygenase and phospholipase-A2

Summary The present work investigates the possibility that lipoxygenase products are involved in the biochemical mechanisms of blastocyst implantation by utilizing nordihydroguaiaretic acid (NDGA) and caffeic acid (CA), inhibitors of lipoxygenase enzymes, and quinacrine (QU), an inhibitor of phospholipase-A₂. It has been shown previously that inhibition of cyclooxygenase results in blockade of implantation. The inhibitors were dissolved in a standard medium and 5 l of the solutions were micro-injected into the uterine horns of day-4 pregnant mice. The contralateral horns acted as controls and received only vehicle. A sham-operated group provided normal controls. In 14 NDGA-treated mice, the control horns contained 40 implantations while the treated horns contained only 6 small implantations and 8 resorbing sites. These control horns were comparable to the sham controls. In 14 CA-treated mice, treated horns contained 17 small implantations plus 4 resorptions, whereas the control horns contained 26 small implantations and 4 resorptions. Twelve QU-treated mice exhibited 7 small implantations and 4 resorptions in the treated horns, plus 24 small sites and no resorptions in the control horns. Fourteen sham-operated mice had 95 implantation sites and no resorptions in their 28 horns. The results provide evidence for the involvement of the lipoxygenase enzymes and phospholipase-A₂ in the initial implantation process and in the subsequent development of early pregnancy.     

双氧水对叶片延迟发光的影响

采用生物超微弱发光探测技术对不同浓度的双氧水(H2O2)胁迫下植物叶片的延迟发光、超氧物歧化酶(SOD)和脂氧合酶(LOX)活性等参数进行了测量和分析.结果表明:所有的浓度都使延迟发光衰减加快,随培养时间的增加,叶片的延迟发光衰减参数1/P的变化先比较缓慢,保持一段时间的相对稳定,然后明显下降;超氧物歧化酶(SOD)活性化整体上是下降的,脂氧合酶(LOX)活性先减小后增加.     

超高压失活大豆脂肪氧合酶数学模型的建立

在对豆浆中脂肪氧合酶的超高压失活动力学进行深入研究的基础上,试图使用两种完全不同的数学模型来描述压力与温度对脂肪氧合酶超高压失活速率常数的影响.研究结果表明:以Hawley提出的热力学方程为基础建立的热动力学数学模型和以Eyring方程为起点建立的经验数学模型都能够成功的用来模拟豆浆中脂肪氧合酶的超高压失活过程.相比之下,热动力学模型要比经验数学模型更加精确.     

Hydra vulgaris ω10-lipoxygenase is used in vivo to synthesize new α-linolenic acid metabolites

Previous studies conducted in cytosolic extracts of the freshwater hydrozoanHydra vulgaris led to the finding of an abundant 11(R)-lipoxygenase catalyzing the peroxidation of polyunsaturated fatty acid (PUFAs) on the tenth carbon atom from the aliphatic end (10 peroxidation). Here we describe experiments aimed at identifying the actual metabolites generated in vivo by such enzymic activity. Homogenates ofH. vulgaris polyps were analyzed by HPLC. This showed the presence of three major components chromatographically identical to three metabolites obtained when incubating the homogenates with exogenous -linolenic acid (-LA). The presence, in extracts of polyps prelabelled with [¹⁴C]--linolenic acid, of radioactive metabolites displaying the same chromatographic properties, substantiated the hypothesis that the natural products isolated in vivo are derived from -LA. Gas chromatographic analyses revealed that this was the most abundant PUFA in both free and phosphoglyceride-bound fatty acid pools. [¹H]-NMR analysis of the endogenous substances, carried out in comparison with products obtained from exogenously incubated -LA, indicated that their structures were those of 9-hydroxy-, 9-hydroperoxy- and 9-keto-octadeca-10E-12Z-15Z-trienoic acids (9--HOTrE,-HPOTrE and-KOTrE).Hydra homogenates transformed 9--HPOTrE partly into 9--HOTrE and partly into 9--KOTrE. Chiral phase HPLC conducted on 9--HOTrE established that this metabolite was composed mostly of theR anantiomer. These observations, and the finding that the presence of exogenous arachidonic acid in incubated homogenates significantly reduces the production of -LA metabolites, provide strong evidence that these compounds are produced by an enzymic activity identical to the previously-describedH. vulgaris (R)-10-lipoxygenase. Further experiments suggested that -LA, acting as the native substrate for this enzyme, is mainly esterified on the 2 position ofHydra phosphoglycerides, and that the production of the -LA metabolites described here for the first time from natural sources, can be potentially enhanced in vivo by stimuli activating phospholipase A₂.     

脂氧合酶--植物抗胁迫响应的关键酶

在植物抗胁迫响应中。脂氧合酶途径在抗性机制中非常重要．脂氧合酶是一种非血红素铁蛋白,在生物体内的主要作用是催化含有顺,顺-1,4-戊二烯结构的多不饱和脂肪酸加合氧分子,生成具有共轭双键的多不饱和脂肪酸的过氧化物及其一系列次生产物,如C3-,C6-,C9-和C12-醛、酮、醇、酸、酯等低分子量易挥发产物。它们和茉莉酸（茉莉酸甲酯）等构成植物抗性系统的信号分子诱导抗性蛋白合成及一系列抗胁迫反应．本文详述了脂氧合酶的结构、特性、作用机理、生理作用、活性测定方法和人工模拟。     

金属拟酶抗逆剂的设计与合成

磷酸酯酶(phosphatases)如紫色酸性磷酸酯酶(purpleacidphosphatase,PAP)、碱性磷酸酯酶(alkalinephosphatase,AP)和各种磷脂酶(phospholipases,PL),氧合酶和氧化酶(oxygenasesandoxidases)如脂氧合酶(lipoxygenase)、多酚氧化酶(polyphenoloxidases),及抗氧化酶,如:超氧化歧化酶(superoxidedismutase,SOD)、过氧化氢酶(catalase,CAT)、过氧化物酶(peroxidase,POD)等是植物防卫系统涉及的重要金属酶(metalloenzymes)和金属激活酶.根据金属酶活性部位结构设计、创制的拟酶化合物含植物必需的微量元素和富咪唑氮的配体,具有抗逆境胁迫(如干旱、寒冷、水渍、盐渍、高温等)和抗病原微生物(如真菌、细菌、病毒等)侵染,及抗早衰能力,提高作物产量5.1%～49.41%.这种仿生配合物性质稳定,抗性广谱,防、治作用兼备;安全、低毒(半数致死量LD50≥600～5000mg/kg);分子量小,膜透性好;高效(使用浓度4～20mg·L-1,用量小,每公顷全生长期仅用3～15g);因系化学仿生化合物,可进行规模化生产.最近,首次证明一种含铜模型化合物[Cu(EDTB)](NO3)2·EtOH和水稻稻瘟病、纹枯病病原体诱导产生的植物抗毒素(Phytoalexin,PA)一样,诱导磷脂水解产生不饱和脂肪酸及其氧化次级产物,这或许是含铜模型化合物能抗病的原因.植物免疫反应涉     

Occurrence and biosynthesis of 11 (R)-hydroxy-eicosatetraenoic acid (11-R-HETE) in the Caribbean soft coralPlexaurella dichotoma

Gorgonian soft corals from the Caribbean Sea are known to contain prostaglandin-like compounds as well as other products of arachidonic acid lipoxygenation, and the formation of the latter has been suggested to represent the first step in prostaglandin biosynthesis. Here we present evidence for the presence of 11-R-hydroxy-5Z, 8Z, 12E, 14Z-eicosatetraenoic acid (11-R-HETE), as well as of the enzyme responsible for its biosynthesis, in the Caribbean gorgonianPlexaurella dichotoma. Lipid extracts fromP. dichotoma were purified by conventional SiO₂ column chromatography followed by reversed phase high-pressure liquid chromatography (HPLC). These yielded a component having chromatographic and spectroscopic properties identical to synthetic 11-HETE. Electron impact mass spectrometric analysis of the acetoxy-, methyl ester derivative of the compound confirmed its identity as 11-HETE, while chiral phase HPLC of the methyl ester derivative showed that the stereochemistry of the alcoholic carbon atom wasR. Enzymatically active homogenates fromP. dichotoma were able to convert both unlabelled and [³H] arachidonic acid into 11-HETE. In vitro biosynthesis of the latter metabolite was also observed with homogenates of the Mediterranean gorgonianParamuricea clavata, another non-prostaglandin-containing soft coral, thus suggesting that 11-R-HETE production is not necessarily accompanied by prostaglandin formation in gorgonian corals.