植物血红素加氧酶研究进展

本文综述了血红素加氧酶（HO）的催化机理、结构特征、遗传学突变体以及在光敏色素发色团合成、调控根形态发生和参与植物对非生物胁迫应答中的作用及信号转导。同时,介绍了紫外线和盐胁迫等逆境条件以及生长素和脱落酸等植物激素对HO基因表达调控等方面的研究进展。     

膜脂与植物的抗寒性

低温是限制植物分布及其生物产量的重要环境因素,也是危害农业生产的主要自然灾害之一。从１７７８年Ｂｉｅｒｋａｎｄｅｒ报导８种植物在１－２℃低温下死亡现象至今,已有许多科学工作者对植物的寒害机理进行了研究,并提出了“生理干旱”（Ｓａｃｈｓ,１８６４）、“饥饿”（Ｍｏｌｉｓｃｈ,１８９６）、“代谢失调”和“毒物积累”等假说。这些假说从不同角度反映了植物发生冷害原因,但都有一定的片面性。随后的一些研究者对植物的几种冷害生理反应出现的时间顺序进行了比较研究,指出有毒物质积累和代谢活动失调都不是冷害的原初反…     

植物鞘脂的结构、代谢途径及其功能

众所周知, 鞘脂是生物膜结构的重要组成成分, 随着鞘脂在动物和酵母中的深入研究发现, 鞘脂及其代谢产物是一类很重要的活性分子, 它们参与调节细胞的生长、分化、衰老和细胞程序性死亡等许多重要的信号转导过程。鞘脂在植物中的研究最近几年才开始, 植物鞘脂的功能还不十分清楚。最近的研究发现, 鞘脂及其代谢产物在植物中也起着很重要的信号分子作用。该文详细总结了鞘脂在植物中的结构、代谢途径和主要生物学功能, 并结合实验室的工作对植物鞘脂的功能研究进行了展望。     

植物鞘脂的结构、代谢途径及其功能

众所周知,鞘脂是生物膜结构的重要组成成分,随着鞘脂在动物和酵母中的深入研究发现,鞘脂及其代谢产物是一类很重要的活性分子,它们参与调节细胞的生长、分化、衰老和细胞程序性死亡等许多重要的信号转导过程。鞘脂在植物中的研究最近几年才开始,植物鞘脂的功能还不十分清楚。最近的研究发现,鞘脂及其代谢产物在植物中也起着很重要的信号分子作用。该文详细总结了鞘脂在植物中的结构、代谢途径和主要生物学功能,并结合实验室的工作对植物鞘脂的功能研究进行了展望。     

特异切割12-脂加氧酶mRNA的核酶体外活性及动力学研究

根据锤头状核酶(Ribozyme)的作用模式,设计、合成并克隆了特异性切割12-脂加氧酶(12-LO)mRNA的核酶基因。以合成的25个核苷酸长的12-脂加氧酶RNA片段为底物与转录的核酶RNA一起保温检测其体外切割活性。实验结果表明,在37℃保温时,核酶在体外对12脂加氧酶具有较高的特异切割活性,其Km值为1300 nmol/L,其kcat值为0.083/min,在50℃保温时,核酶具有很高的切割活性,其kcat值为0.31/min。     

植物的脂氢过氧化物裂解酶

介绍植物脂氢过氧化物裂解酶(HPL)的生化性质以及相关的分子生物学特性和生理功能的研究进展,并对其在植物遗传改良中的应用前景作了评述.     

膜脂过氧化对植物细胞的伤害

本文综述了近年来有关膜脂过氧化对植物细胞膜系统的结构和功能、细胞的蛋白质代谢、光合作用和呼吸作用等过程的伤害机理方面的研究进展。     

植物脂氧合酶研究进展

脂氧合酶（简称LOX）是广泛分布的含有非血红素离子的双加氧酶,它是植物十八碳酸代谢途径的关键酶．该途径也称LOX途径。因为该酶作用的产物在植物的生长发育过程中以及在植物对环境胁迫反应中起着重要的作用,因此一直是人们研究的热点。目前对于植物脂氧舍酶的研究主要集中在脂氧合酶基因的表达调控、LOX途径的生化研究以及代谢产物的生理功能这几个方面。     

植物非特异脂转移蛋白的研究

综述了植物抗菌蛋白nsL TPs的研究进展：植物抗菌蛋白nsL TPs是一类对细菌、真菌等微生物有抑制或杀灭作用的蛋白质：它们的抗菌能力强,有较好的耐热性,抗菌机理独特,在农业生产上有着广泛的应用前景。     

植物脂肪氧合酶的生理作用

脂氧合酶广泛地存在于植物特别是高等植物体内,在植物离体的叶、果实和种子中含有较高的活力。如人类广泛食用的大豆,由于大豆种子中含有产生豆腥味的活性物质,对大豆蛋白制品的营养和风味产生极为不利的影响。人们发现豆腥味产生的原因是多元不饱和脂肪酸的酶促氧化所致,其中的关键酶即为脂肪氧化酶,当时命名为Lipoxidase,但后来发现该酶还有另外一种功能即与类胡萝卜素的降解有关,称为胡萝卜素氧化酶(Carotene oxidase),如在小麦面粉中掺入少量大豆粉,可以使面团漂白,并     

植物种子脂氧合酶

概述了植物种子脂氧合酶蛋白和编码其基因的特性、各种突变体及其遗传规律、基因表达和调控以及生理功能的研究进展.     

The Antigenicity of Lipoxygenase from Various Plant Sources

Lipoxygenase enzymes isolated from soya bean, potato and egg-plantare antigenic, and precipitate with their specific antibodies.All three enzymes have common determinants, since there is cross-reactionamong them. Each of the enzymes is strongly inhibited by antibodiesof soya bean and potato lipoxy-genase. Some of the determinantsare heat stable (to 100 °C) and can compete after heat treatmentwith the same determinants of the natural enzyme for the sameantibody. The peptides which carry the determinant to whichthe antibody is bound, causing inhibition of enzymatic activityof soya bean and egg-plant lipoxygenase, have been isolated. It is likely that the active site is not identical with anyof the antigenic determinants, but it is certainly close toone or several of them. Thus the specific antibody causes sterichindrance of the active site.     

Role of Tomato Lipoxygenase D in Wound-Induced Jasmonate Biosynthesis and Plant Immunity to Insect Herbivores

In response to insect attack and mechanical wounding, plants activate the expression of genes involved in various defense-related processes. A fascinating feature of these inducible defenses is their occurrence both locally at the wounding site and systemically in undamaged leaves throughout the plant. Wound-inducible proteinase inhibitors (PIs) in tomato (Solanum lycopersicum) provide an attractive model to understand the signal transduction events leading from localized injury to the systemic expression of defense-related genes. Among the identified intercellular molecules in regulating systemic wound response of tomato are the peptide signal systemin and the oxylipin signal jasmonic acid (JA). The systemin/JA signaling pathway provides a unique opportunity to investigate, in a single experimental system, the mechanism by which peptide and oxylipin signals interact to coordinate plant systemic immunity. Here we describe the characterization of the tomato suppressor of prosystemin-mediated responses8 (spr8) mutant, which was isolated as a suppressor of (pro)systemin-mediated signaling. spr8 plants exhibit a series of JA-dependent immune deficiencies, including the inability to express wound-responsive genes, abnormal development of glandular trichomes, and severely compromised resistance to cotton bollworm (Helicoverpa armigera) and Botrytis cinerea. Map-based cloning studies demonstrate that the spr8 mutant phenotype results from a point mutation in the catalytic domain of TomLoxD, a chloroplast-localized lipoxygenase involved in JA biosynthesis. We present evidence that overexpression of TomLoxD leads to elevated wound-induced JA biosynthesis, increased expression of wound-responsive genes and, therefore, enhanced resistance to insect herbivory attack and necrotrophic pathogen infection. These results indicate that TomLoxD is involved in wound-induced JA biosynthesis and highlight the application potential of this gene for crop protection against insects and pathogens.     

Lipoxygenase pathways of macrophages

Resident mouse peritoneal macrophages when exposed to zymosan during the first day of cell culture synthesize and secrete large amounts of prostaglandin E2 and leukotriene (LT) C4, the respective products of cyclooxygenase- and 5-lipoxygenase-catalyzed oxygenations of arachidonic acid. Under these conditions of cell stimulation only small amounts of hydroxyeicosatetraenoic acids (HETEs) are concomitantly produced. However, exogenously added arachidonic acid is metabolized to large amounts of 12- and 15-HETE. No LTC4 is formed under these conditions. Inasmuch as 12- and 15-HETE have been shown to modulate certain lymphocyte responses, further study of the regulation of their production by macrophages is warranted.     

Study on Soybean Lipoxygenase

Some β-bisabolene derivatives, III, XX, XXVII and XXVIII, were synthesized and shown to possess the juvenile hormone activity.     

植物脂氧合酶蛋白特性及其在果实成熟衰老和逆境胁迫中的作用

脂氧合酶（lipoxygenase,LOx）作为植物脂肪酸氧化途径的关键酶,是多基因家族,在植物生长发育中起重要作用。本文综述了脂氧合酶的蛋白结构特征、催化反应的位置特异性、分类及其代谢途径,重点介绍了LOX代谢途径中的氢过氧化物裂解酶（hydropemxide lyase,HPL）支路和丙二烯氧化物合酶（allene oxide synthase,AOS）支路,最后阐述了LOxs在植物成熟衰老和逆境胁迫中的作用,为通过基因工程手段改善果实品质以及提高植物抗逆性提供了一定的理论依据。     

Lipoxygenase activity during parabolic flights

Experiments in Space clearly show that various cellular processes, such as growth rates, signaling pathways and gene expression, are modified when cells are placed under conditions of weightlessness. As yet, there is no coherent explanation for these observations, though recent experiments, showing that microtubule self-organization is gravity-dependent suggest that investigations at the molecular level might fill the gap between observation and understanding of Space effects. Lipoxygenases are a family of dioxygenases which have been implicated in the pathogenesis of several inflammatory conditions, in atherosclerosis, in brain aging and in HIV infection. In plants, lipoxy-genases favour germination, participate in the synthesis of traumatin and jasmonic acid and in the response to abiotic stress. Here, we took advantage of a fibre optics spectrometer developed on purpose, the EMEC (Effect of Microgravity on Enzymatic Catalysis) module, to measure the dioxygenation reaction by pure soybean lipoxygenase-1 (LOX-1) during the 28th parabolic flight campaign of the European Space Agency (ESA). The aim was to ascertain whether microgravity can affect enzyme catalysis.     

Lipoxygenase heterogeneity in Pisum sativum

Antibodies raised against two pea (Pisum sativum L. cv. Birte) seed lipoxygenases have been used to analyze lipoxygenase heterogeneity in seeds and in other organs. At least seven different polypeptides were identified in vivo; five of these were identified as precursors synthesized in vitro. The developmental appearance of the seed polypeptides has been analyzed and early and late forms were identified. Limited N-terminal sequence data indicated further heterogeneity when compared with sequences predicted from cDNAs.Abbreviations cDNA complementary DNA - DAF days after flowering - HPLC high-performance liquid chromatography - Ig immunoglobulin - kb kilobase - M_r relative molecular mass - PAGE polyacrylamide gel electrophoresis - PVDF polyvinylidene difluoride - SDS sodium dodecyl sulphate - SSC 0.15 M sodium chloride, 0.015 M sodium citrate, pH 7.0 This work was supported by the Agricultural and Food Research Council via a grant-in-aid to the John Innes Institute. We acknowledge financial support from the Commission of the European Communities Biotechnology Action Programme; grant No. 0063-UK.