Antimutagenic activity of Armoracia rusticana, Zea mays and Ficus carica plant extracts and their mixture

Antimutagenic action of plant extracts of Armoracia rusticana, Ficus carica, Zea mays and their mixture on environmental xenobiotics has been investigated. The plant extracts and their mixture decreased the level of mutations induced by N-metil-N'-nitro-N-nitrozoguanidin (MNNG) in Vicia faba cells, chlorophyll mutations in Arabidopsis thaliana and NaF induced mutability in rat marrow cells. The studied plant extracts and their mixture demonstrate the ability to decrease the genotoxicity of environmental mutagens.     

A novel beta-glucosidase from the cell wall of maize (Zea mays L.): rapid purification and partial characterization.

Plants have a variety of glycosidic conjugates of hormones, defense compounds, and other molecules that are hydrolyzed by beta-glucosidases (beta-D-glucoside glucohydrolases, E.C. 3.2.1.21). Workers have reported several beta-glucosidases from maize (Zea mays L.; Poaceae), but have localized them mostly by indirect means. We have purified and partly characterized a 58-Ku beta-glucosidase from maize, which we conclude from a partial sequence analysis, from kinetic data, and from its localization is not identical to any of those already reported. A monoclonal antibody, mWP 19, binds this enzyme, and localizes it in the cell walls of maize coleoptiles. An earlier report showed that mWP19 inhibits peroxidase activity in crude cell wall extracts and can immunoprecipitate peroxidase activity from these extracts, yet purified preparations of the 58 Ku protein had little or no peroxidase activity. The level of sequence similarity between beta-glucosidases and peroxidases makes it unlikely that these enzymes share epitopes in common. Contrary to a previous conclusion, these results suggest that the enzyme recognized by mWP19 is not a peroxidase, but there is a wall peroxidase closely associated with the 58 Ku beta-glucosidase in crude preparations. Other workers also have co-purified distinct proteins with beta-glucosidases. We found no significant charge in the level of immunodetectable beta-glucosidase in mesocotyls or coleoptiles that precedes the red light-induced changes in the growth rate of these tissues.     

Peroxidase and IAA-oxidase in crude and partially purified enzyme extracts of growing and differentiating root cells

Crude enzyme extracts from the zones of division, elongation and differentiation of cells of primary maize (Zea mays) root show peroxidase activity but lack IAA-oxidase activity. After partial purification of the extracts by gel filtration on Sephadex G-25, the specific peroxidase activity increases almost twice and a high IAA-oxidase activity appears. The partial purification of the enzyme extracts does not change the electrophoretic pattern of the peroxidase isoenzymes, but significantly improves the separation and the visualization of isoenzymes with IAA-oxidase activity. The data obtained were interpreted in connection with the different modifying effect of the low molecular compounds (mainly phenolics) on the activity and the isoenzyme patterns of the peroxidase and the IAA-oxidase.     

Identification of enzymically inactive apocytochrome c peroxidase in anaerobically grown Saccharomyces cerevisiae.

Anaerobically grown yeast cells lack cytochrome c peroxidase activity but rapidly acquire it upon aeration. In order to study the oxygen-induced formation of this hemoprotein, extracts of anaerobic and aerobic yeast cells were resolved by one- and two-dimensional acrylamide gel electrophoresis and the separated polypeptides were then checked for comigration with radiolabeled purified cytochrome c peroxidase from aerobic cells or for reaction with cytochrome c peroxidase antiserum. Both types of extracts contained roughly equal amounts of a polypeptide which was indistinguishable from apocytochrome c peroxidase with respect to antigenicity, isoelectric point, and apparent molecular weight in three different gel systems. In confirmation of an earlier report by Sels. A.A., and Cocriamont, C. (1968) (Biochem. Biophus. Res. Commun. 32, 192-198) the oxygen-induced formation of cytochrome c peroxidase was insensitive to inhibitors of protein synthesis and could be mimicked by the addition of heme to extracts of anaerobic cells. We conclude that the oxygen-induced formation of yeast cytochrome c peroxidase involves the addition of heme to the apoenzyme which is already present in the anaerobically grown cells.     

Localization of nitrite and sulfite reductase in bundle sheath and mesophyll cells of maize leaves

The distribution of nitrite reductase (EC 1.7.7.1) and sulfite reductase (EC 1.8.7.1) between mesophyll ceils and bundle sheath cells of maize ( Zea mays L. cv. Seneca 60) leaves was examined. This examination was complicated by the fact that both of these enzymes can reduce both NO-₂ and SO^2-₃ In crude extracts from whole leaves, nitrite reductase activity was 6 to 10 times higher than sulfite reductase activity. Heat treatment (10 min at 55°C) caused a 55% decrease in salfite reductase activity in extracts from bundle sheath cells and mesophyll cells, whereas the loss in nitrite reductase activity was 58 and 82% in bundle sheath cells and mesophyll cell extracts, respectively. This result was explained, together with results from the literature, by the hypothesis that sulfite reductase is present in both bundle sheath cells and mesophyll cells, and that nitrite reductase is restricted to the mesophyll cells. This hypothesis was tested i) by comparing the distribution of nitrite reductase activity and sulfite reductase activity between bundle sheath and mesophyll cells with the presence of the marker enzymes ribulose-l, 5-bisphosphate carboxylase (EC 4.1.1.39) and phosphoe-nolpyruvate carboxylase (EC 4.1.1.32), ii) by examining the effect of cultivation of maize plants in the dark without a nitrogen source on nitrite reductase activity and sulfite reductase activity in the two types of cells, and iii) by studying the action of S^2-on the two enzyme activities in extracts from bundle sheath and mesophyll cells. The results from these experiments are consistent with the above hypothesis.     

Soybean Seed Coat Peroxidase (A Comparison of High-Activity and Low-Activity Genotypes)

Peroxidase activity in the seed coats of soybean (Glycine max [L.] Merr.) is controlled by the Ep locus. We compared peroxidase activity in cell-free extracts from seed coat, root, and leaf tissues of three EpEp cultivars (Harosoy 63, Harovinton, and Coles) to three epep cultivars (Steele, Marathon, and Raiden). Extracts from the seed coats of EpEp cultivars were 100-fold higher in specific activity than those from epep cultivars, but there was no difference in specific activity in crude root or leaf extracts. Isoelectric focusing of root tissue extracts and staining for peroxidase activity showed that EpEp cultivars had a root peroxidase of identical isoelectric point to the seed coat peroxidase, whereas roots of the epep types were lacking that peroxidase, indicating that the Ep locus may also affect expression in the root. In seed coat extracts, peroxidase was the most abundant soluble protein in EpEp cultivars, whereas this enzyme was present only in trace amounts in epep genotypes, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Histochemical localization of peroxidase activity in seed coats of EpEp cultivars shows that the enzyme occurs predominately in the cytoplasm of hourglass cells of the subepidermis. No obvious difference in the gross or microscopic structure of the seed coat was observed to be associated with the Ep locus. These results suggest that soybean seed coat peroxidase may be involved in processes other than seed coat biosynthesis.     

Immunohistochemical detection of human gastrointestinal glutathione peroxidase in normal tissues and cultured cells with novel mouse monoclonal antibodies.

This is the first report to describe the successful detection of human gastrointestinal glutathione peroxidase in normal tissues by Western blotting and immunohistochemical staining techniques. Four hybridoma clones producing monoclonal antibodies (MAbs) against the human gastrointestinal glutathione peroxidase were established from mice immunized with a gastrointestinal glutathione peroxidase-derived peptide. The MAbs did not crossreact with other members of the glutathione peroxidase family, be it cellular glutathione peroxidase, phospholipid hydroperoxide glutathione peroxidase, or extracellular glutathione peroxidase. Although the MAbs were found to react with a 24-kD protein in a Western blotting assay using gastric carcinoma cell extracts as antigen, they did not react with a B-lymphoblastoid cell extract. Immunohistochemical staining showed gastrointestinal glutathione peroxidase localized in the cytoplasm and in the nucleus of gastric carcinoma cells. Moreover, gastrointestinal glutathione peroxidase was detected in tissue extracts of human stomach, small intestine, large intestine, liver, and gallbladder by Western blotting, and its localization was immunohistochemically confirmed in the mucosal epithelia of the basal area of gastric pits and intestinal crypts.     

Deficient metabolic utilization of hydrogen peroxide in Trypanosoma cruzi.

The glutathione peroxidase-glutathione reductase system, an alternative pathway for metabolic utilization of H2O2 [Chance, Sies & Boveris (1979) Physiol. Rev. 59, 527-605], was investigated in Trypanosoma cruzi, an organism lacking catalase and deficient in peroxidase [Boveris & Stoppani (1977) Experientia 33, 1306-1308]. The presence of glutathione (4.9 +/- 0.7 nmol of reduced glutathione/10(8) cells) and NADPH-dependent glutathione reductase (5.3 +/- 0.4 munit/10(8) cells) was demonstrated in the cytosolic fraction of the parasite, but with H2O2 as substrate glutathione peroxidase activity could not be demonstrated in the same extracts. With t-butyl hydroperoxide or cumene hydroperoxide as substrate, a very low NADPH-dependent glutathione peroxidase activity was detected (equivalent to 0.3-0.5 munit of peroxidase/10(8) cells, or about 10% of glutathione reductase activity). Blank reactions of the glutathione peroxidase assay (non-enzymic oxidation of glutathione by hydroperoxides and enzymic oxidation of NADPH) hampered accurate measurement of peroxidase activity. The presence of superoxide dismutase and ascorbate peroxidase activity in, as well as the absence of catalase from, epimastigote extracts was confirmed. Ascorbate peroxidase activity was cyanide-sensitive and heat-labile, but no activity could be demonstrated with diaminobenzidine, pyrogallol or guaiacol as electron donor. The summarized results support the view that T. cruzi epimastigotes lack an adequate enzyme defence against H2O2 and H2O2-related free radicals.     

Immunological characteristics of PEP carboxylase from leaves of C3-, C4- and C3-C4 intermediate species of Alternanthera--comparison with selected C3- and C4- plants

Immunological cross-reactivity of phosphoenolpyruvate carboxylase (PEPC) in leaf extracts of C3-, C4- and C3-C4 intermediate species of Alternanthera (along with a few other C3- and C4- plants) was studied using anti-PEPC antibodies raised against PEPC of Amaranthus hypochondriacus (belonging to the same family as that of Alternanthera, namely Amaranthaceae). Antibodies were also raised in rabbits against the purified PEPC from Zea mays (C4- monocot-Poaceae) as well as Alternanthera pungens (C4- dicot-Amaranthaceae). Monospecificity of PEPC-antiserum was confirmed by immunoprecipitation. Amount of PEPC protein in leaf extracts of A. hypochondriacus could be quantified by single radial immunodiffusion. Cros- reactivity of PEPC in leaf extracts from selected C3-, C4-, and C3-C4 intermediate species (including those of Alternanthera) was examined using Ouchterlony double diffusion and Western blots. Anti-PEPC antiserum raised against A. hypochondriacus enzyme showed high cross-reactivity with PEPC in leaf extracts of A. hypochondriacus or Amaranthus viridis or Alternanthera pungens (all C4 dicots), but limited cross-reactivity with that of Zea mays, Sorghum or Pennisetum (all C4 monocots). Interestingly, PEPC in leaf extracts of Alternanthera tenella, A. ficoides, Parthenium hysterophorus (C3-C4 intermediates) exhibited stronger cross-reactivity (with anti-serum raised against PEPC from Amaranthus hypochondriacus) than that of Pisum sativum, Commelina benghalensis, Altenanthera sessilis (C3 plants). Further studies on cross-reactivities of PEPC in leaf extracts of these plants with anti-PEPC antisera raised against PEPC from leaves of Zea mays or Alternanthera pungens confirmed two points--(i) PEPC of C3-C4 intermediate is distinct from C3 species and intermediate between those of C3- and C4-species; and (ii) PEPC of C4-dicots was closer to that of C3-species or C3-C4 intermediates (dicots) than to that of C4-monocots.     

Authentic processing and targeting of active maize auxin-binding protein in the baculovirus expression system.

The major auxin-binding protein (ABP1) from maize (Zea mays L.) has been expressed in insect cells using the baculovirus expression system. The recombinant protein can be readily detected in total insect cell lysates by Coomassie blue staining on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Our data suggest that ABP1 is processed similarly in both insect cells and maize. The signal peptide is cleaved at the same position as in maize and the mature protein undergoes tunicamycin-sensitive glycosylation, yielding a product with the same mobility on SDS-PAGE as authentic maize ABP1. On immunoblots the expressed protein is recognized by anti-KDEL monoclonal antibodies. Immunofluorescence localization demonstrates that it is targeted to and retained in the endoplasmic reticulum of insect cells in accordance with its signal peptide and KDEL retention sequence. The expressed ABP1 also appears to be active, since extracts of insect cells expressing ABP1 contain a saturable high-affinity 1-naphthylacetic acid-binding site, whereas no saturable auxin-binding activity is detected in extracts from control cells.     

Purification and Amino-terminal Sequencing of a 68 kD Glycopolypeptide of the Plasma Membrane from Maize Sperm Cells

Based on author's previous work on detection and immunolocalization of glycoproteins of the plasma membrane of maize ( Zea mays L. ) sperm cells, a 68 kD peripheral specific glycopolypeptide of the plasma membrane from maize sperm cells was purified by IEF-SDS two-dimensional electrophoresis. It presents specif- ically positive reaction in Con A-HRP (concanavalin A-horseradish peroxidase) staining, and its pi value is 5.5. The search in protein sequence database reveals that the amino-terminal sequence of this glycopolypeptide is identical with that of Con A. But its difference from Con A in molecular weight and pi value indicates that it could be related to a Con A receptor on the plasma membranes of maize sperm cells instead of being Con A itself. It is fascinating to study further the function of the above glycopolypeptide in gametic recognition, adhesion and fusion of the double fertilization in maize.     

胡椒、芒果和黄皮的化感作用潜力

以胡椒、芒果和黄皮作为供体,玉米、黄豆、南瓜、花生、萝卜、稗草、马唐、柱花草为受体,通过种子萌发法和根生长法测定胡椒、芒果和黄皮的化感作用潜力.结果表明,玉米、黄豆、南瓜、稗草和马唐的萌发和根生长都受到3种供体水浸提液的影响,3种供体水浸提液在高浓度下抑制而在低浓度下则促进受体的萌发和根生长;胡椒和芒果根系周围的土壤对玉米萌发和根生长有促进作用而对花生的萌发和根生长则有抑制作用.3种供体的水浸提液通过乙酸乙酯、正丁醇萃取分离成不同极性的三相后分别对玉米、萝卜和柱花草进行处理.结果表明,胡椒和芒果浸提液的水相与正丁醇相对受体的抑制作用明显强于乙酸乙酯相,表明胡椒和芒果的化感物质具有较强的极性.     

反枝苋水浸提液与挥发油对黄瓜根尖的影响

采用悬空气法研究了在入侵植物反枝苋(Amaranthus retroflexus L.)水浸提液和挥发油作用下,黄瓜根缘细胞活性、根冠果胶甲基酯酶(PME)、根尖过氧化氢酶(CAT)、过氧化物酶(POD)、超氧化物歧化酶(SOD)以及丙二醛(MDA)含量的变化规律.结果表明:反枝苋水浸提液对黄瓜根的生长无显著性影响而挥发油显著抑制黄瓜根的生长,且随浓度增大抑制作用显著增强.PME活性随着水浸提液浓度的增大呈先上升后下降趋势,而随着挥发油浓度的升高呈现逐渐上升的趋势;水浸提液和挥发油均降低了对根缘细胞的存活率,这种抑制作用随浓度的增加而增大;随着处理液浓度增大,黄瓜根尖中MDA含量、CAT活性整体表现为增加,SOD活性先升高后降低,POD活性与对照差异不显著.反枝苋挥发油的化感效应大于水浸提液的化感效应.     

Distribution of two isoforms of glutamine synthetase in bundle sheath and mesophyll cells of corn leaves

Localization of two isoforms of glutamine synthetase (GS; EC 6.3.1.2) was investigated in different cell types, mesophyll cells and bundle sheath cells, of corn ( Zea mays L. var. W64A × W182E) leaves by using ion exchange chrotnatography. In whole leaf extracts, relative activities of GS1 (cytosolic GS) and GS2 (chloroplastic GS) were almost equal. Purified mesophyll protoplasts and bundle sheath strands also showed similar proportions of GS1 and GS2. Methionine sulfoximine (1 mM ) enhanced the accumulation of ammonia when mesophyll protoplasts were incubated with nitrite or when bundle sheath strands were incubated with glycine. This clearly indicates a spatial separation of metabolism of NH⁺₄ derived from photorespiration and from reduction of NOJ.     

Localization and Characterization of Peroxidases in the Mitochondria of Chilling-Acclimated Maize Seedlings

We present evidence of two peroxidases in maize (Zea mays L.) mitochondria. One of these uses guaiacol and the other uses cytochrome c as the electron donor. Treatments of fresh mitochondria with protease(s) indicate that ascorbate and glutathione peroxidases are likely bound to the mitochondria as cytosolic contaminants, whereas guaiacol and cytochrome peroxidases are localized within the mitochondria. These two mitochondrial peroxidases are distinct from contaminant peroxidases and mitochondrial electron transport enzymes. Cytochrome peroxidase is present within the mitochondrial membranes, whereas guaiacol peroxidase is loosely bound to the mitochondrial envelope. Unlike other cellular guaiacol peroxidases, mitochondrial guaiacol peroxidase is not glycosylated. Digestion of lysed mitochondria with trypsin activated mitochondrial guaiacol peroxidase but inhibited cytochrome peroxidase. Isoelectric focusing gel analysis indicated guaiacol peroxidase as a major isozyme (isoelectric point 6.8) that is also activated by trypsin. No change in the mobility of guaiacol peroxidase due to trypsin treatment on native polyacrylamide gel electrophoresis was observed. Although both peroxidases are induced by chilling acclimation treatments (14[deg]C), only cytochrome peroxidase is also induced by chilling (4[deg]C). Because chilling induces oxidative stress in the maize seedlings and the mitochondria are a target for oxidative stress injury, we suggest that mitochondrial peroxidases play a role similar to catalase in protecting mitochondria from oxidative damage.     

The recA+ gene product is more important than catalase and superoxide dismutase in protecting Escherichia coli against hydrogen peroxide toxicity.

Various deoxyribonucleic acid repair-deficient strains of Escherichia coli K-12 were exposed to hydrogen peroxide under anaerobic conling of the strains was determined. The level of catalase, peroxidase, and superoxide dismutase in cell-free extracts of the strains as well as the capacity of intact cells to decompose hydrogen peroxide were assayed, recA strains were more rapidly killed than other strains with deoxyribonucleic acid repair deficiencies. There was no correlation between the killing rate of the strains and the capacity of intact cells to decompose hydrogen peroxide or the level of catalase and superoxide dismutase in cell-free extracts. The level of peroxidase in cell-free extract was too low to be determined.     

Screening of medicinal plant extracts for antioxidant activity

The methanol extracts of nine medicinal plants traditionally used in Chinese medicine were screened for antioxidant activity versus resveratrol, which has been shown to protect cells from oxidative damage [Toxicol. Lett. 102 (1998) 5]. Most of the plant extracts used in this study inhibited the H(2)O(2)-induced apoptosis of Chinese hamster lung fibroblast (V79-4) cells. The extracts of Areca catechu var. dulcissima, Paeonia suffruticosa, Alpinia officinarum, Glycyrrhiza uralensis and Cinnamomun cassia strongly enhanced viability against H(2)O(2)-induced oxidative damage in V79-4 cells. Relatively high levels of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity were detected in extracts of Areca catechu var. dulcissima, Paeonia suffruticosa and Cinnamomun cassia (IC(50) < 6.0 microg/ml). The activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) were dose-dependently enhanced in V79-4 cells treated with most of the plant extracts. The extracts of Areca catechu var. dulcissima showed higher antioxidant activity than resveratrol in all experiments. These results suggest that the plant extracts prevent oxidative damage in normal cells probably because of their antioxidant characteristics.     

壳聚糖对镉胁迫下玉米幼苗叶片AsA-GSH循环的调控效应

以玉米（Zea mays L.）品种‘郑单958’为实验材料,分析外施壳聚糖对镉胁迫下玉米幼苗生物量、叶片镉含量、叶片超氧阴离子（O₂^·-）产生速率和过氧化氢（H₂O₂）的含量,以及抗坏血酸-谷胱甘肽（AsA-GSH）循环中抗氧化酶的活性及抗氧化物含量的影响。结果显示,随着镉胁迫时间的延长,玉米幼苗发生氧化胁迫,叶片抗氧化酶（APX、GR、DHAR、MDHAR）活性和抗氧化物（AsA、GSH）的含量降低,镉积累过量会抑制玉米幼苗的生长。施加壳聚糖可以降低镉胁迫下玉米幼苗叶片O₂^·-的产生速率和H₂O₂含量,提高上述抗氧化酶活性和抗氧化物的含量,促进AsA和GSH的再生,维持细胞的氧化还原状态,促进玉米幼苗的生长。研究结果表明壳聚糖处理后玉米幼苗保持了较高的AsA-GSH循环运作效率,提高了抗氧化能力,可有效缓解镉胁迫对玉米幼苗生长的抑制。     

Methodological approaches for studying apoplastic redox activity: 1. Mechanisms of peroxidase release

It was demonstrated the efficiency of the application of extracellular solution, i.e., the leachate derived from roots after their incubation, for the analysis of apoplastic redox enzymes (exemplified by peroxidase) in the roots of 5-day-old seedlings of spring wheat (Triticum aestivum L., cv. Kazanskaya yubileinaya) after wounding stress. Such non-invasive approach allows the studying of enzymes without a disruption of plant tissue. The inhibitory analysis showed that newly synthesized and pre-existing in the cells peroxidases were not released from the cytoplasm at stress conditions. The proposed methodological approach for obtaining the enzymatic extracts of apoplastic redox enzymes opens up broad prospects for researches of plant immunity and stress responses.     

青蒿过氧化物酶的克隆及其在体外对青蒿素生物合成的影响

用RACE方法从青蒿(Artemisia annua L.)高产株系001中克隆了一个过氧化物酶.将此基因在大肠杆菌BL21(DE3)pLysS细胞中进行原核表达得到重组蛋白(APOD1),表达的蛋白分别以抗坏血酸、愈创木酚为底物进行过氧化反应,结果显示,APOD1催化愈创木酚的活力是抗坏血酸的1.8倍左右,由此表明,克隆的APOD1类属于植物经典过氧化物酶(第三大类过氧化物酶).经与其他植物过氧化物酶同源性比较分析,推测APOD1的氨基酸序列与白羽扇豆(Lupinus albus)、辣根菜(Armoracia rusticana)、小麦(Triticum aestivum)、烟草(Nicotiana tabacum)和蕃茄(Lycopersicon esculentum)的一致性分别为42.0%、36.2%、38.9%、33.6%和32.8%.Northern杂交分析表明,此基因在青蒿的根、茎和叶中均有表达.加入APOD1至青蒿细胞提取液有利于青蒿酸向青蒿素的生物转化,但APOD1并不能直接以青蒿酸作为氧化底物.