四棱豆不同生育期叶片中过氧化物酶活力测定

比较了四棱豆不同生育期叶片中过氧化物酶活性,结果表明：该酶活力和比活力在不同生育期存在着明显差异,蛋白质含量变化不大。在成熟期,随着植株节位升高,酶活力及比活力均呈下降趋势,蛋白质含量则呈上升趋势。     

一种烟粉虱成虫唾液酶鉴定与活性分析的方法

以B型烟粉虱Bemisia tabaci(Gennadius)成虫为材料,介绍了一种微型刺吸式昆虫唾液酶鉴定和分析的方法,主要包括人工饲养、唾液收集、唾液多酚氧化酶(PPO)和过氧化物酶(POD)的鉴定与活性分析。结果显示,B型烟粉虱在特异性嗜好寄主甘蓝上分泌的多酚氧化酶与过氧化物酶的比活力分别为嗜好寄主番茄上的1.54和1.65倍。该方法操作简捷,鉴定结果直观清晰,酶活测定灵敏,适合于其他微型刺吸式昆虫如蚜虫、木虱等的唾液酶研究。     

修饰血红素提高血红蛋白类过氧化物酶活性

利用苯酚或对羟基联苯对血红蛋白的血红素辅基进行化学修饰,将修饰后的血红素与脱辅基血红蛋白进行重组得到新的血红蛋白。以光吸收扫描分析修饰血红素和重组血红蛋白,证明新的重组血红蛋白构建成功。酶活力测定表明,修饰血红素得到的重组血红蛋白的类过氧化物酶活性都比天然血红蛋白的酶活力高,用对羟基联苯修饰血红素得到的重组血红蛋白的酶活提高明显,约是天然血红蛋白的1.6倍。     

麦红吸浆虫滞育发生和解除过程中保护酶活力动态

采用保护酶活性测试盒分别测定了麦红吸浆虫滞育前、滞育期及滞育解除后过氧化物酶（POD）、超氧化物歧化酶（SOD）和过氧化氢酶（CAT）等3种保护酶的活力.结果表明：幼虫从老熟到进入滞育的初期,3种保护酶的活力均呈下降趋势.滞育年周期中,SOD和CAT活力对环境温度的反应相同,即低温促进其活力升高,高温导致其活力下降;POD活力与环境温度和滞育发育有关;整个滞育期间,裸露幼虫和结茧幼虫3种保护酶的活力随季节变化趋势相同,但同期的裸露幼虫活力略高于结茧幼虫;不同滞育年限幼虫3种保护酶的活力差异不显著.滞育解除后,3种保护酶的活力均随生长发育进程逐渐升高.     

电离辐射对有核红细胞表面腺三磷去焦磷酸酶活力的影响

(1)两栖类(黑斑蛙),爬行类(鳖),鸟类(家鸽)有核红细胞表面Apyrase活力具有显著差异,鳖最高,黑斑蛙次之,而以家鸽为最低。(2)经30,000或50,000 rads X射线离体照射后,家鸽红细胞表面Apyrase活力分别下降18%与27%,鳖则为7%及13%,而黑斑蛙红细胞表面的Apyrase却并未发生明显的变化。因此,不同动物有核红细胞表面Apyrase,对电离辐射的敏感程度似与动物系统上的高低有关,而与原来酶活的高低无关。     

香荚兰成熟荚果中三种酶的活性测定

不同级别的香荚兰 (Vanillaplanifolia)成熟荚果以及其中的种子和肉质果壳中的 β -葡萄糖甙酶、过氧化物酶和多酚氧化酶的活性研究结果表明高等级的果荚中过氧化物酶活性高于低等级的果荚 ,种子中的 β -葡萄糖苷酶活性几乎达到肉质果荚的 2倍 ;过氧化物酶的活性主要分布在果壳中 ,没有在种子中测过氧化物酶的活性 ;多酚氧化酶的活性在测定样品极低 ,未能测出。     

壬基酚对黑斑蛙神经活动的影响

应用电生理的方法研究不同浓度壬基酚对黑斑蛙的坐骨神经干神经冲动产生和传导的影响。用不同浓度的壬基酚处理黑斑蛙,7 d后,观察其活动状态和体表特征,同时用生物信号采集处理系统分别测定壬基酚对黑斑蛙坐骨神经干的神经冲动传导速度、动作电位幅度、相对不应期和绝对不应期的影响。结果表明：随着壬基酚浓度的增加,黑斑蛙的活力减弱,其皮肤出现血斑的现象加重,说明壬基酚可引起黑斑蛙活力、精神和体表等发生异常;随着壬基酚浓度的升高,黑斑蛙坐骨神经干的神经冲动传导速度逐渐减慢,动作电位峰值降低,相对不应期和绝对不应期逐渐延长,与壬基酚浓度呈剂量-效应关系。说明在壬基酚作用下,黑斑蛙神经活动对刺激反应的灵敏性降低,动作电位的产生及传导受到一定程度的抑制和阻碍。在50 mg·kg^-1低浓度组,壬基酚对黑斑蛙神经活动影响不显著(P>0.05),说明黑斑蛙对低浓度的壬基酚有一定的耐受力。     

亚硒酸钠对小麦幼苗中谷胱甘肽过氧化物酶和谷胱甘肽转硫酶活性以及谷胱甘肽含量的影响

用1.0 mg·L-1的亚硒酸钠根施小麦幼苗,测定亚硒酸钠对谷胱甘肽过氧化物酶和谷胱甘肽转硫酶活性以及还原性谷胱甘肽含量的结果表明,外源亚硒酸钠对麦苗地上部的谷胱甘肽过氧化物酶和谷胱甘肽转硫酶活性均有诱导作用,使麦苗体内的谷胱甘肽含量水平增加.     

黑斑蛙精巢MDA和抗氧化酶对铅、镉暴露的生态毒性响应

以健康性成熟黑斑蛙为供试动物,以精巢组织丙二醛(MDA)含量、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和谷胱甘肽过氧化物酶(GSH-Px)活性为指标,进行了水体铅、镉暴露的生态毒性响应研究.结果表明:(1)精巢MDA含量随铅、镉暴露浓度的升高而明显增加,且呈明显的浓度-效应关系.说明低水平铅、镉的长期暴露对黑斑蛙精巢具有一定的损伤作用;(2)SOD活性在各处理组响应变化不明显,CAT、GSH-Px活性则被显著诱导,说明GSH-Px、CAT在铅、镉引起的精巢抗氧化损伤中起着重要作用;(3)3种抗氧化酶相比,GSH-Px活性对铅、镉暴露响应最敏感,SOD活性的响应最不明显,精巢GSH-Px活性是指示铅、镉暴露的优选生物标志物。     

外源ABA对低温胁迫水稻过氧化物酶同工酶的影响

采用聚丙烯酰胺垂直板电泳法,就外源ABA对低温胁迫下水稻幼苗过氧化物酶（POD）同工酶的影响进行了研究。结果表明,低温胁迫下,水稻幼苗长势明显下降,与其相应的过氧化物酶同工酶也发生了变化,外施ABA(10^-5mol/L）提高了水稻幼苗的抗寒能力,其相应的过氧化物酶同工酶却表现为部分酶活性增强,说明：（1）过氧化物同工酶的变化将引起植物对低温的抗性反应;（2）外源ABA引起自由基清除酶（如POD）活力的升高,是植物抗寒性增强的原因之一。     

Indoleacetic Acid Oxidase: A Dual Catalytic Enzyme?

The isolation of a unique enzyme capable of oxidizing indoleacetic acid, but devoid of peroxidase activity, has been reported for preparations from tobacco roots and commercial horseradish peroxidase. Experiments were made to verify these results using enzyme obtained from Betula leaves and commercial horseradish peroxidase. Both indoleacetic acid oxidase and guaiacol peroxidase activity appeared at 2.5 elution volumes from sulfoethyl-Sephadex. These results were obtained with both sources of enzyme. In no case was a separate peak of indoleacetic acid oxidase activity obtained at 5.4 elution volumes as reported for the tobacco enzyme using the same chromatographic system. Both types of activity, from both sources of enzyme, also eluted together during gel filtration. Successful column chromatography of Betula enzyme was dependent upon previous purification by membrane ultrafiltration. These results indicate indoleacetic acid oxidase activity and guaiacol peroxidase activity are dual catalytic functions of a single enzyme.     

Adsorption of peroxidase on Celite 545 directly from ammonium sulfate fractionated white radish (Raphanus sativus) proteins

This paper demonstrates the direct immobilization of peroxidase from ammonium sulfate fractionated white radish proteins on an inorganic support, Celite 545. The adsorbed peroxidase was crosslinked by using glutaraldehyde. The activity yield for white radish peroxidase was adsorbed on Celite 545 was 70% and this activity was decreased and remained 60% of the initial activity after crosslinking by glutaraldehyde. The pH and temperature-optima for both soluble and immobilized peroxidase was at pH 5.5 and 40°C. Immobilized peroxidase retained higher stability against heat and water-miscible organic solvents. In the presence of 5.0 mM mercuric chloride, immobilized white radish peroxidase retained 41% of its initial activity while the free enzyme lost 93% activity. Soluble enzyme lost 61% of its initial activity while immobilized peroxidase retained 86% of the original activity when exposed to 0.02 mM sodium azide for 1 h. The K_m values were 0.056 and 0.07 mM for free and immobilized enzyme, respectively. Immobilized white radish peroxidase exhibited lower V_max as compared to the soluble enzyme. Immobilized peroxidase preparation showed better storage stability as compared to its soluble counterpart.     

Purification and thermal characterization of a novel peroxidase from a local chick pea cultivar

A novel peroxidase isolated from a local chick pea (Cicer arietinum L.) cultivar (Balksar 2000) was purified by means of ammonium sulfate precipitation, DEAE-cellulose chromatography and two runs on gel filtration. The purified enzyme has a specific activity of 2045 U/mg with 17 % activity recovery. The molecular mass of the enzyme was estimated to be 39 kDa by SDS-polyacrylamide gel electrophoresis. Optimum pH and temperature of the enzyme were 5.5 and 45 degrees C respectively. The thermal denaturation of local chick pea peroxidase was studied in aqueous solution at temperatures ranging from 45 degrees C to 65 degrees C. The temperature of 50% inactivation of the enzyme was found to be 68 degrees C. The enthalpy (DeltaH*) and free energy (DeltaG*) of thermal denaturation of chick pea peroxidase were 101.4 and 103.4 k J/mol respectively at 65 degrees C.Metals like Zn2+, Mn2+, Hg2+, Co2+ and Al3+ slightly inhibited the peroxidase activity while Ca2+, Mg2+ and Ba2+ have no effect on enzyme activity. The high specific activity and thermal stability make chick pea peroxidase an alternative to horseradish peroxidase (HRP) in various applications.     

Controlled layer-by-layer immobilization of horseradish peroxidase.

Horseradish peroxidase (HRP) was biotinylated with biotinamidocaproate N-hydroxysuccinimide ester (BcapNHS) in a controlled manner to obtain biotinylated horseradish peroxidase (Bcap-HRP) with two biotin moieties per enzyme molecule. Avidin-mediated immobilization of HRP was achieved by first coupling avidin on carboxy-derivatized polystyrene beads using a carbodiimide, followed by the attachment of the disubstituted biotinylated horseradish peroxidase from one of the two biotin moieties through the avidin-biotin interaction (controlled immobilization). Another layer of avidin can be attached to the second biotin on Bcap-HRP, which can serve as a protein linker with additional Bcap-HRP, leading to a layer-by-layer protein assembly of the enzyme. Horseradish peroxidase was also immobilized directly on carboxy-derivatized polystyrene beads by carbodiimide chemistry (conventional method). The reaction kinetics of the native horseradish peroxidase, immobilized horseradish peroxidase (conventional method), controlled immobilized biotinylated horseradish peroxidase on avidin-coated beads, and biotinylated horseradish peroxidase crosslinked to avidin-coated polystyrene beads were all compared. It was observed that in solution the biotinylated horseradish peroxidase retained 81% of the unconjugated enzyme's activity. Also, in solution, horseradish peroxidase and Bcap-HRP were inhibited by high concentrations of the substrate hydrogen peroxide. The controlled immobilized horseradish peroxidase could tolerate much higher concentrations of hydrogen peroxide and, thus, it demonstrates reduced substrate inhibition. Because of this, the activity of controlled immobilized horseradish peroxidase was higher than the activity of Bcap-HRP in solution. It is shown that a layer-by-layer assembly of the immobilized enzyme yields HRP of higher activity per unit surface area of the immobilization support compared to conventionally immobilized enzyme.     

Induction of enzymatic scavengers of active oxygen species in rice in response to infection by <Emphasis Type="Italic">Rhizoctonia solani</Emphasis>

Changes in the activities of peroxidase, ascorbate peroxidase, catalase and superoxide dismutase in rice in response to infection by Rhizoctonia solani were studied. A significant increase in peroxidase activity was observed in R. solani-inoculated rice leaf sheaths 1 day after inoculation and the maximum enzyme activity was recorded 3 days after inoculation at which period a 3-fold increase in peroxidase activity was observed compared to the untreated control. Three peroxidase isozymes viz., PO-4, PO-5 and PO-6 were induced in rice upon infection by R. solani. Ascorbate peroxidase and catalase activities significantly increased 1–2 days after inoculation and the maximum enzyme activities were recorded 5 days after inoculation. Superoxide dismutase activity increased significantly 2 days after inoculation and increased progressively, reaching four times the control value at 7 days after inoculation.     

Peroxidase refolding in the presence of specific antibodies

A panel of eight monoclonal antibodies raised against horseradish root peroxidase has been assembled and characterized. Affinity constants were determined for all antibodies, and their specificity for various structural forms of the enzyme (native peroxidase, apoperoxidase, and denatured peroxidase) were assessed by competitive enzyme immunoassay. The effects of the antibodies on the process of refolding of peroxidase after its denaturing with 6.5 M guanidine hydrochloride were studied spectrophotometrically, by the restoration of the enzymatic activity in the reaction of 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonate). The yield of the active enzyme in the course of the refolding was increased 1.5 to 1.7 times in the presence of antibody H1. Effects of the antibodies constituting the panel on the activity of native peroxidase and the stability of its dilute solutions were analyzed.     

Calcium alginate–starch hybrid support for both surface immobilization and entrapment of bitter gourd (Momordica charantia) peroxidase

Calcium alginate–starch hybrid gel was employed as an enzyme carrier both for surface immobilization and entrapment of bitter gourd peroxidase. Entrapped crosslinked concanavalin A–bitter gourd peroxidase retained 52% of the initial activity while surface immobilized and glutaraldehyde crosslinked enzyme showed 63% activity. A comparative stability of both forms of immobilized bitter gourd peroxidase was investigated against pH, temperature and chaotropic agent; like urea, heavy metals, water-miscible organic solvents, detergent and inhibitors. Entrapped peroxidase was significantly more stable as compared to surface immobilized form of enzyme. The pH and temperature-optima for both immobilized preparations were the same as for soluble bitter gourd peroxidase. Entrapped crosslinked concanavalin A–bitter gourd peroxidase showed 75% of the initial activity while the surface immobilized and crosslinked bitter gourd peroxidase retained 69% of the original activity after its seventh repeated use.     

The tyrosinase activity of melanosomes from the harding-passey melanoma: The absence of a peroxidase component in vitro

Melanosomes were isolated from the Harding-Passey melanoma with a density gradient technique. Using the Pomerantz radioassay for tyrosinase activity it was found that these isolated melanosomes could hydroxylate tyrosine in the presence of catalase sufficient to deny the enzyme any hydrogen peroxide. It was further found that the rate of hydroxylation was unaffected by the presence of exogenous hydrogen peroxide. Tyrosinase activity could be suppressed by preincubation in diethyldithiocarbamate followed by removal of this inhibitor before enzyme assay. Attempts to regain enzymatic activity, however, by addition of copper II ions were unsuccessful. No peroxidase activity could be detected on the isolated granules, and indeed evidence for a peroxidase inhibitor on the granules was found. It was also found that the peroxidase activity present in a 20% homogenate of mouse muscle did not demonstrate any tyrosinase activity with the Pomerantz assay even in the presence of hydrogen peroxide. It is concluded from these studies that there is tyrosinase on these melanosomes which is capable in vitro of hydroxylating tyrosine without any contribution from an active peroxidase.     

Studies of Peroxidase Refolding in the Presence of Specific Antibodies

A panel of eight monoclonal antibodies raised against horseradish root peroxidase was assembled and characterized. Affinity constants were determined for all antibodies, and their specificity for various structural forms of the enzyme (native peroxidase, apoperoxidase, and denatured peroxidase) were assessed by competitive enzyme immunoassay. The effects of the antibodies on the process of refolding of peroxidase after its denaturing with 6.5 M guanidine chloride were studied spectrophotometrically, by the restoration of the enzymatic activity in the reaction of 2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonate) oxidation. The yield of the active enzyme in the course of the refolding was increased by 1.5–1.7 times in the presence of antibody H1. Effects of the antibodies constituting the panel on the activity of native peroxidase and the stability of its dilute solutions were analyzed.