花生叶片衰老过程中某些酶活性的变化

人们对花生叶片衰老的现象早就有所认识 ,认为叶片变黄脱落、叶斑病加重是花生叶片衰老的主要特征 ,但真正对花生叶片衰老的研究较少且意见不一。Ｋｖｉｅｎ和Ｏｚｉａｓ Ａｋｉｎｓ( 1 991 )认为花生播后1 46ｄ(饱果期 )叶片仍未表现衰老迹象 ,叶中Ｎ含量仍保持 2 8ｍｇ/ｇ的较高水平 ;Ｓａｈｒａｗａｔ等 ( 1 987)研究发现 ,随着花生叶片的衰老 ,叶片中Ｎ、Ｐ、Ｋ、Ｃｕ、Ｍｎ、Ｚｎ的含量逐渐降低 ,而叶片中Ｍｇ的含量有增加趋势 ,Ｃａ的含量随衰老明显升高。Ｎａｒａｙａｎａｎ和Ｃｈａｎｄ( 1 986)研究指出 ,花生主茎上、下叶片叶比重 …     

不同粒型品种花生开花后叶片中几种保护酶活性的变化

不同类型品种花生叶片的CAT活性变化趋势一致 ,均于花后 2 7d达到高峰 ,花后 6 7d之前小粒型 >大粒型 >中粒型 ,之后为大粒型 >中粒型 >小粒型 ;POD活性于花后 37d和 77d达到高峰 ,酶活性表现为中粒型 >小粒型 >大粒型 ,且中粒型品种变化剧烈 ;SOD活性表现为大粒型 >中粒型 >小粒型。荚果发育前期 ,CAT和SOD活性高 ,发育后期POD活性高。大粒型品种保护酶SOD起主要作用 ,小粒型品种POD和CAT起主要作用 ,中粒型品种介于两者之间     

BA对花生叶片蔗糖和淀粉代谢有关酶活性的影响

用１０－５ｍｏｌ／ＬＢＡ处理去顶去根花生幼苗库叶２４ｈ内．蔗糖磷酸合成酶和细胞质果糖－１,６－二磷酸酯酶活性逐渐增加．酸性转化酶活性降低．使蔗糖含量提高,α－淀粉酶活性的增强,促进淀粉分解。ＢＡ处理２４ｈ后,随着蔗糖磷酸合成酶和细胞质果糖－１．６－二磷酸酯酶活性的减弱．酸性转化酶活性逐渐增加．蔗糖含量减少,有利光合碳在淀粉的积累．     

钙对水杨酸诱导番茄叶片灰霉病抗性及防御酶活性的影响

以番茄‘L402’品种幼苗为试材,经水杨酸(SA)诱导处理后接种灰霉病菌,再进行外源Ca2+、Ca2+螯合剂和Ca2+抑制剂处理,分析Ca2+和SA处理番茄叶片对灰霉病抗性和主要防御酶系活性的变化,探讨Ca2+和SA对番茄诱导抗病性的影响。结果显示:(1)外源SA可显著提高番茄诱导叶和非诱导叶抗灰霉病能力,Ca2+能进一步增强SA诱导的抗病能力;而Ca2+螯合剂EGTA和质膜钙通道抑制剂LaCl3则不同程度地抑制了SA诱导的番茄灰霉病抗性。(2)外源SA能提高番茄诱导叶和非诱导叶中苯丙氨酸解氨酶(PAL)、多酚氧化酶(PPO)、过氧化物酶(POD)活性,外源Ca2+亦进一步增强了SA诱导的上述防御酶活性,但缺钙处理则不同程度降低这些防御酶活性。(3)外源补充Ca2+及不同缺钙处理对SA诱导的过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性未发现规律性影响。研究表明,钙对SA诱导番茄抗灰霉病性的增强效应,可能与其提高SA诱导番茄叶片中PAL、PPO和POD等防御酶活性有关。     

不同钙素水平对厚皮甜瓜叶片光合作用和保护酶活性的影响

采用深液流无土栽培方式,研究不同钙素水平对厚皮甜瓜叶片光合作用和保护酶活性的影响。结果表明,在缺钙、低钙、高钙胁迫下,厚皮甜瓜叶片中的叶绿素和类胡萝卜素含量明显下降,叶绿素a/叶绿素b比值升高;同时叶片中的超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)的活性及丙二醛(MAD)含量、相对电导率、可溶性蛋白质含量都明显高于正常供钙的植株。缺钙胁迫下,基础荧光(Fo)下降,低钙和高钙胁迫下Fo 升高,但缺钙、低钙、高钙胁迫下叶片叶绿素荧光参数Fv/Fm、Fv/Fo、Fm、Yield和ETR都明显下降。缺钙胁迫下叶片净光合速率(Pn)、气孔导度(Gs)下降,胞间 CO2 浓度(Ci)升高;而高钙胁迫下 Pn、Gs 下降的同时,Ci 也相应下降,表明缺钙胁迫下的光合抑制主要是由于非气孔限制引起,而高钙胁迫下的光合抑制主要是由于气孔限制引起。     

钙对玉米幼苗谷胱甘肽还原酶活性的影响

CaCl2浸种或酶提取液中加入CaCl2均可显著提高两品种玉米幼苗中谷胱甘肽还原酶（GR）活性,且不同钙盐对GR的激活效应基本相同。Ca^2 专一螯合剂EGTA浸种或加入到酶提取液中则可显著抑制GR活性,表明GR活性至少部分受Ca^2 调控。     

小麦叶片酸性磷酸酯酶活性及缺磷对它的影响

在盆栽和大田条件下,小麦最上一片展开叶酸性磷酸酯酶活性前期低、后期高;叶位越高,酶活性越低;缺磷导致酶活性升高;酶活性与体内无机磷、有机磷、全磷含量及籽粒产量呈显著负相关。     

DPC浸种对花生幼苗根系和叶片生理功能的影响

在田间条件下,研究了DPC浸种对花生（Arachis hypogaeaL.)幼苗根系和叶片生理功能的影响。结果表明,DPC可提高花生幼苗根系中IAA和Z ZR的含量,促进根系的生长,提高根系活力;DPC可促进花生苗期叶片叶绿素的合成,提高叶绿素含量,提高苗期叶片的光合速率。在实践中,用150mg/LDPC浸种是取得花生壮苗丰产的有效措施。     

PP333对花生生长和叶片结构的影响

以不同浓度的氯乙唑（Paclobutrazol.PP333)溶液施用于5叶期的花生幼苗,施方法分为喷施和土施。地上部施用部位又分为涂叶和涂茎,40天后测量植株生长,蒸腾速率和气孔阻力,观察叶片结构,结果表明：1．PP333抑制花生主茎的生长,减少地上部分干重,对根部干重无影响甚至略增,根茎比增大,气孔阻力大,蒸腾速率下降,贮水细胞体积增大,这些解剖和生物特征,有利于抵抗水分胁迫,2．PP3333可使叶片表皮细胞变小,叶绿体的基粒片层数目少,基质片层也稀疏,抑制叶绿体发育。3．土施PP333对花生生长抑制效应比喷施显著得多,根部吸收的抑制效果最大,茎部居中,叶片最不明显。     

钾对小麦旗叶蔗糖和籽粒淀粉积累的影响

 利用冬小麦品种‘鲁麦22’(Triticum aestivum cv. `Lumai 22’)在大田条件下研究了钾素对小麦旗叶蔗糖和籽粒淀粉积累及其有关酶活性的影响。结果表明,钾素有利于提高旗叶光合速率,增强开花后旗叶磷酸蔗糖合成酶活性,提高旗叶中蔗糖的含量;从而提高了灌浆期间籽粒中蔗糖的供应,增强了籽粒中蔗糖合成酶和腺苷二磷酸葡萄糖焦磷酸化酶的活性,加速了淀粉积累速率,提高了粒重和产量。     

MLC-kinase/phosphatase control of Ca2+ signal transduction in airway smooth muscles

In airway smooth muscles, kinase/phosphatase-dependent phosphorylation and dephosphorylation of the myosin light chain (MLC) have been revealed by many authors as important steps in calcium (Ca²⁺) signalling pathway from the variation of Ca²⁺ concentration in cytosol to the force development. Here, a theoretical analysis of the control action of MLC-kinase (MLCK) and MLC-phosphatase (MLCP) in Ca²⁺ signalling is presented and related to the general control principles of these enzymes, which were previously studied by Reinhart Heinrich and his co-workers. The kinetic scheme of the mathematical model considers interactions among Ca²⁺, calmodulin (CaM) and MLCK and the well-known 4-state actomyosin latch bridge model, whereby a link between them is accomplished by the conservation relation of all species of MLCK. The mathematical model predicts the magnitude and velocity of isometric force in smooth muscles upon transient biphasic Ca²⁺ signal. The properties of signal transduction in the system such as the signalling time, signal duration and signal amplitude, which are reflected in the properties of force developed, are studied by the principles of the metabolic control theory. The analysis of our model predictions confirms as shown by Reinhart Heinrich and his co-workers that MLCK controls the amplitude of signal more than its duration, whereas MLCP controls both. Finally, the simulations of elevated total content of MLCK, a typical feature of bronchial muscles of asthmatic subjects and spontaneously hypertensive rats as well as potentiation of MLCP catalytic activity, are carried out and are discussed in view of an increase in the force magnitude.     

Slaving the cytochrome P-450 dependent monooxygenase system by periodically applied light pulses

The light-induced enhancement of 7-ethoxycoumarin-O-deethylase activity was measured in a reconstituted system consisting of the enzyme P-450 II B1 (P-450_PB-B) and the NADPH-cytochrome P-450 reductase. The phases of the catalytic cycle of 2 · 10¹² protein complexes were locked by periodic application of light pulses (0.1 s duration, 1.2–2.5 s repetition time, and 390–470 nm 0.27 Joule/nmol P-450). More than 80% of the active reconstituted enzyme complexes worked in phase if the repetition time (1.32 s) was slightly smaller than the catalytic cycle time of the free running enzyme (1.54 s). The percentage of synchronized enzyme complexes as a function of the repetition time is shown. It is shown that the lifetime of the product-enzyme complex is shortened by the light.Abbreviations P-450 liver microsomal cytochrome P-450 - PB phenobarbitalOffprint requests to: H. Gruler     

Continuous degradation of maltose by enzyme entrapment technology using calcium alginate beads as a matrix

Maltase from Bacillus licheniformis KIBGE-IB4 was immobilized within calcium alginate beads using entrapment technique. Immobilized maltase showed maximum immobilization yield with 4% sodium alginate and 0.2 M calcium chloride within 90.0 min of curing time. Entrapment increases the enzyme–substrate reaction time and temperature from 5.0 to 10.0 min and 45 °C to 50 °C, respectively as compared to its free counterpart. However, pH optima remained same for maltose hydrolysis. Diffusional limitation of substrate (maltose) caused a declined in V_max of immobilized enzyme from 8411.0 to 4919.0 U ml^?1 min^?1 whereas, K_m apparently increased from 1.71 to 3.17 mM ml^?1. Immobilization also increased the stability of free maltase against a broad temperature range and enzyme retained 45% and 32% activity at 55 °C and 60 °C, respectively after 90.0 min. Immobilized enzyme also exhibited recycling efficiency more than six cycles and retained 17% of its initial activity even after 6th cycles. Immobilized enzyme showed relatively better storage stability at 4 °C and 30 °C after 60.0 days as compared to free enzyme.     

陆生植物体内酶系统对UV-B辐射增强的响应

臭氧层减薄导致地表中波紫外线UV-B(280～320 nm)辐射的增强,UV-B辐射能量远高于可见光,且能被植物体内蛋白质和核酸等生物大分子吸收.酶是植物体内起催化作用的一类蛋白质,酶的数量和活性对UV-B辐射增强有强烈的响应.本文将近年来增强UV-B辐射对植物体内酶影响的研究工作进行了综述.主要包括抗氧化酶、核酮糖-1,5-二磷酸羧化酶、硝酸还原酶和谷氨酰胺合成酶.并就今后该方面的研究提出建议.     

Increase in glutamate synthase (NADH) activity in maize seedlings in response to nitrate and ammonium nitrogen

Roots and leaves of Zea mays L. cv. Ganga Safed-2 seedlings grown with nutrient solution containing either 10 m M KNO₃ or NH₄Cl or 5 m M NH₄NO₃ had considerably higher glutamate synthase (NADH, EC 1.4.1.14) activity than the corresponding organs from seedlings grown without any nitrogen. The supply of inorganic nitrogen for a short time, i.e. 3 h, to roots and leaves excised from seedlings grown without nitrogen also increased the enzyme activity in these organs. This increase was more pronounced with nitrate than with ammonium nitrogen. When excised roots and leaves from NH₄NO₃-grown seedlings were incubated in a minus nitrogen medium for 24 h, the enzyme activity declined considerably. This decline was inhibited to some extent by nitrogen, especially by nitrate. Inorganic nitrogen prevented similarly the decline in in vitro enzyme activity during 24 h storage at 25°C, more regularly for the root than for the leaf enzyme. The experiments demonstrate the role of inorganic nitrogen in the regulation of glutamate synthase activity.     

烟叶主要生物酶活性变化规律及其在烟叶发酵中的应用

烟叶中的生物酶在烟叶的生长及发酵过程中起着重要作用.他们能够促进烟叶内部有机物质的分解与转化,调整烟叶中各种化学成分的比例,提高烟叶中香气成分的形成和积累,从而提高烟叶的综合品质.综述了烟叶生长、加工过程中淀粉酶、蛋白酶、多酚氧化酶的活性变化规律,以及外加生物酶在烟叶发酵中的应用现状.     

Glutamate 90 at the Luminal Ion Gate of Sarcoplasmic Reticulum Ca2+-ATPase Is Critical for Ca2+ Binding on Both Sides of the Membrane

The roles of Ser⁷², Glu⁹⁰, and Lys²⁹⁷ at the luminal ends of transmembrane helices M1, M2, and M4 of sarcoplasmic reticulum Ca²⁺-ATPase were examined by transient and steady-state kinetic analysis of mutants. The dependence on the luminal Ca²⁺ concentration of phosphorylation by P_i (“Ca²⁺ gradient-dependent E2P formation”) showed a reduction of the apparent affinity for luminal Ca²⁺ in mutants with alanine or leucine replacement of Glu⁹⁰, whereas arginine replacement of Glu⁹⁰ or Ser⁷² allowed E2P formation from P_i even at luminal Ca²⁺ concentrations much too small to support phosphorylation in wild type. The latter mutants further displayed a blocked dephosphorylation of E2P and an increased rate of conversion of the ADP-sensitive E1P phosphoenzyme intermediate to ADP-insensitive E2P as well as insensitivity of the E2·BeF₃⁻ complex to luminal Ca²⁺. Altogether, these findings, supported by structural modeling, indicate that the E2P intermediate is stabilized in the mutants with arginine replacement of Glu⁹⁰ or Ser⁷², because the positive charge of the arginine side chain mimics Ca²⁺ occupying a luminally exposed low affinity Ca²⁺ site of E2P, thus identifying an essential locus (a “leaving site”) on the luminal Ca²⁺ exit pathway. Mutants with alanine or leucine replacement of Glu⁹⁰ further displayed a marked slowing of the Ca²⁺ binding transition as well as slowing of the dissociation of Ca²⁺ from Ca₂E1 back toward the cytoplasm, thus demonstrating that Glu⁹⁰ is also critical for the function of the cytoplasmically exposed Ca²⁺ sites on the opposite side of the membrane relative to where Glu⁹⁰ is located.     

Characterization of the calcium paradox in the isolated perfused frog heart: enzymatic,ionic, contractile and electrophysiological studies

Summary The effect of perfusion temperature and duration of calcium deprivation on the occurrence of the calcium paradox was studied in the isolated frog heart. Loss of electrical and mechanical activity, ion fluxes, creatine kinase and protein release were used to define cell damage. Perfusion was performed at 22, 27, 32, and 37°C, and calcium deprivation lasted 10, 20, 30, or 40 min. At 22°C and 27°C even a prolonged calcium-free perfusion failed to induce a calcium paradox. After 30 min of calcium-free perfusion at 37°C ventricular activity ceased and a major contraction occurred followed by an increase in resting tension. During the 15-min re-perfusion period the release of creatine kinase was 158.24±2.49 IU·g dry wt^-1, and the total amount of protein lost was 70.37±0.73 mg·g dry wt^–1, while lower perfusion temperatures resulted in a decreased loss of protein and creatine kinase. Ion fluxes in the perfusion effluent indicate that during re-perfusion a massive calcium influx accompanied by a potassium and a magnesium efflux, and an apparent sodium efflux, occur at a perfusion temperature of 37°C after 30 min of calcium deprivation. The results suggest that the basic principles and damaging effects of calcium overloading are common to both mammalian and frog hearts.