Glycolate metabolism and subcellular distribution of glycolate oxidase in Spatoglossum pacificum (Phaeophyceae, Chromophyta)

Seven enzymes participating in glycolate metabolism were demonstrated to be present in crude extract of the brown alga Spatoglossum pacificum Yendo. These were phosphoglycolate phosphatase, glycolate oxidase, glutamate-glyoxylate aminotransferase, serine hydroxymethyltransferase, amino acid-hydroxy-pyruvate aminotransferase, hydroxypyruvate reductase and catalase. Malate synthase, which is involved in glycolate metabolism in the xanthophycean alga, could not be detected. On demonstration of subcellular distribution of glycolate oxidizing enzymes by linear sucrose density gradient centrifugation, glycolate oxidase was detected in the same fraction at a density of 1.23 g cm^?3 with catalase: that is, the marker enzyme of peroxisome and serine hydroxymethyltransferase was found in the same fraction at a density of 1.21 g cm^?3 with isocitrate dehydrogenase, the marker of mitochondria. From the present data, it is proposed that the brown alga Spatoglossum possesses the ability to metabolize glycolate to glycerate via the pathway which may be similar to that of higher plants.     

Substrate specificity and activities of glyoxylate and hydroxyypyruvate reductases from leaf extracts: differentiation by ammonium sulfate fractionation and by immunoprecipitation

Leaf extracts from seven monocotyledonous and dicotyledonous species contained considerable levels of NADPH-dependent glyoxylate- and hydroxypyruvate reductase activities. These activities ranged from 0.02 to 0.22 μmol (mg protein)⁻¹ min⁻¹. For all plants tested, the glyoxylate reductase (GR) activity, assayed with either NADPH or NADH, was sensitive to inhibition by acetohydroxamate, a glycine analogue. Hydroxypyruvate reductase (HPR) activities were unaffected by acetohydroxamate. Differential precipitation of soluble leaf proteins of spinach, pea and barley by ammonium sulfate (0–45% and 45–60% saturation) indicated the presence of at least three distinct reductases, which differed in their specificities for glyoxylate, hydroxypyruvate and NAD(P)H. For all species, the NADH-dependent HPR-activity was almost completely precipitated by low ammonium sulfate concentration (45%), while precipitation of the NADPH-GR, NADH-GR and, to some extent, NADPH-HPR activities required 60% ammonium sulfate. The NADPH-dependent GR and HPR activities had high affinity for glyoxylate and hydroxypyruvate, respectively, as indicated by low apparent K_m values of 40–120 μ M . The occurrence of at least three distinct reductases utilizing hydroxypyruvate and/or glyoxylate as substrate was supported by antibody-precipitation studies using antibodies prepared against NADH(NADPH)-HPR, the well-known peroxisomal enzyme that also shows non-specific GR activity. These data are discussed with respect to recent reports on the purification and characterization of NADPH(NADH)-GR, and NADPH (NADH)-HPR, two cytosolic reductases, and the role is assessed for these enzymes in reducing hydroxypyruvate and glyoxylate that may be leaked from peroxisomes.     

NCS对离体萝卜子叶微体中酶活性及细胞超微结构的影响

研究了天然生物活性物质narciclasine(NCS)对离体萝卜子叶光下生长发育期间叶绿素含量变化、异柠檬酸裂解酶及羟基丙酮酸还原酶活性的影响;并对萝卜子叶细胞的超微结构变化进行了观察。结果表明,NCS明显抑制光下培养的离体萝卜子叶叶绿素含量及鲜重增加,对异柠檬酸裂解酶及羟基丙酮酸还原酶活性也显示出明显的抑制作用。电镜观察显示,NCS对蛋白体及脂质体的降解、叶绿体的发育也表现出强烈的抑制效应。NCS的各种抑制作用均随其浓度的增加而增加,而且高浓度的NCS(10^-5mol／L)基本上完全阻止了离体萝卜子叶的光下生长及其转绿。     

Alleviation of NaCl Stress by Pretreatment with Phytohormones in Vigna radiata

Efficiency of pretreatment as foliar spray of indole-3-acetic acid, gibberellic acid and kinetin, each ranging from 0.1 to 10.0 μM concentration, in restoring the metabolic alterations imposed by NaCl salinity was investigated in Vigna radiata (L.) Wilczek. Glycolate oxidase, superoxide dismutase, catalase and peroxidase activities increased under stress in leaves and roots also. Malondialdehyde content and total peroxide content also increased under stress. All the three hormones used were able to overcome to variable extents the adverse effects of stress imposed by NaCl to these parameters. This revised version was published online in July 2006 with corrections to the Cover Date.     

Antioxidant enzyme activities in subcellular fractions of larvae of the black swallowtail butterfly,Papilio polyxenes

The black swallowtail butterfly, Papilio polyxenes, larvae are specialized feeders of pro-oxidant rich plants of Apiaceae and Rutaceae. An important defense against toxic forms of oxygen species generated by ingestion of the pro-oxidants, are the antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), GSH-dependent glutathione peroxidases (selenium-dependent glutathione peroxidase [GPOX] and peroxidase activity of selenium-independent glutathione-S-transferase [GT_px]), and glutathione reductase (GR). The subcellular distribution of these enzymes in black swallowtail larvae was investigated and was found to resemble the patterns described for larvae of two other lepidopteran species: the southern armyworm, Spodoptera eridania, and the cabbage looper, Trichoplusia ni. The confinement of SOD in the cytosol and mitochondria was typically eukaryotic, but the relative proportion (1:1) was markedly different from the mammalian pattern (4:1; cytosol:mitochondria). The most obvious difference between the black swallowtail and other lepidoptera as a group, and mammalian species, is in very wide intracellular distributions of CAT, GTpx, and GR in insect species. Insects possess very low levels of a GPOX-like activity which reduces both H₂O₂ and organic peroxides. Consequently, insects have elaborate activities with a wide subcellular distribution of both CAT which decomposes H₂O₂, and GTpx which decomposes organic peroxides. The reduction of peroxides is dependent on GSH, which in this process is oxidized to GSSG. GR which reduces GSSG to GSH is also of wide subcellular distribution, analogous to the distribution pattern of GTpx.     

Effect of flooding on the activities of some enzymes of activated oxygen metabolism,the levels of antioxidants,and lipid peroxidation in senescing tobacco leaves

Effects of flooding on the activities of some enzymes of activated oxygen metabolism, the levels of antioxidants, and lipid peroxidation in senescing leaves of tobacco were investigated. As judged by the decrease in chlorophyll and protein levels, flooding accelerated the senescence of tobacco leaves. Total peroxide and the lipid peroxidation product, malondialdehyde, increased in both control and flooding-treated leaves with increasing duration of the experiment. Throughout the duration of the experiment, flooded leaves had higher levels of total peroxide and malondialdehyde than did control leaves. Flooding resulted in an increase in peroxidase and ascorbate peroxidase activities and a reduction of superoxide dismutase activity in the senescing leaves. Glycolate oxidase, catalase, and glutathione reductase activities were not affected by flooding. Flooding increased the levels of total ascorbate and dehydroascorbate. Total glutathione, reduced form glutathione, or oxidized glutathione levels in flooded leaves were lower than in control leaves during the first two days of the experiment, but were higher than in control leaves at the later stage of the experiment. Our work suggests that senescence of tobacco induced by flooding may be a consequence of lipid peroxidation possibly controlled by superoxide dismutase activity. Our results also suggest that increased rates of hydrogen peroxide in leaves of flooded plants could lead to increased capacities of the scavenging system of hydrogen peroxide.Abbreviations GSH reduced form glutathione - GSSG oxidized form glutathione - GSSG reductase glutathione reductase - MDA malondialdehyde - SOD superoxide dismutase     

Variation in the activity of some enzymes of photorespiratory metabolism in C4 grasses

BACKGROUND AND AIMS: Photorespiration occurs in C4 plants, although rates are small compared with C3 plants. The amount of glycine decarboxylase in the bundle sheath (BS) varies among C4 grasses and is positively correlated with the granal index (ratio of the length of appressed thylakoid membranes to the total length of all thylakoid membranes) of the BS chloroplasts: C4 grasses with high granal index contained more glycine decarboxylase per unit leaf area than those with low granal index, probably reflecting the differences in O2 production from photosystem II and the potential photorespiratory capacity. Thus, it is hypothesized that the activities of peroxisomal enzymes involved in photorespiration are also correlated with the granal development. METHODS: The granal development in BS chloroplasts was investigated and activities of the photorespiratory enzymes assayed in 28 C4 grasses and seven C3 grasses. KEY RESULTS: The NADP-malic enzyme grasses were divided into two groups: one with low granal index and the other with relatively high granal index in the BS chloroplasts. Both the NAD-malic enzyme and phosphoenolpyruvate carboxykinase grasses had high granal index in the BS chloroplasts. No statistically significant differences were found in activity of hydroxypyruvate reductase between the C3 and C4 grasses, or between the C4 subtypes. The activity of glycolate oxidase and catalase were smaller in the C4 grasses than in the C3 grasses. Among the C4 subtypes, glycolate oxidase activities were significantly smaller in the NADP-malic enzyme grasses with low granal index in the BS chloroplasts, compared with in the C4 grasses with substantial grana in the BS chloroplasts. CONCLUSIONS: There is interspecies variation in glycolate oxidase activity associated with the granal development in the BS chloroplasts and the O2 production from photosystem II, which suggests different potential photorespiration capacities among C4 grasses.     

The effect of ammonium and nitrate on carbondioxide compensation point and enzymes associated with carbondioxide exchange in wheat

The carbondioxide compensation point (), dry matter production, and the activities of nitrate reductase (NR), glycolate oxidase (GO), ribulose 1,5-bisphosphate carboxylase (RuBPC) and phosphoenolpyruvate carboxylase (PEPC) were measured in wheat, grown on media, containing nitrate or ammonium. Significantly higher and lower dry matter was observed in plants supplied with ammonium-nitrogen (NH₄-N), as compared to those supplied with nitrate-nitrogen (NO₃-N). The activities of NR and PEPC were higher in plants grown on NO₃-N than to those grown on NH₄-N. There were no significant differences in the activities of GO and RuBPC irrespective of whether NO₃-N or NH₄-N was supplied. None of the enzymes was found to be associated directly with the .PEPC activity accounted the measured differences in the and biomass production between NH₄-N and NO₃-N supplied plants. The relationship between PEPC and the is discussed.     

Effect of NaCl stress on H2O2 metabolism in rice leaves

The effect of NaCl stress on H₂O₂ metabolismin detached rice leaves was studied. NaCl (200 mM)treatment did not cause the accumulation ofH₂O₂ and resulted in no increase in lipidperoxidation and membrane leakage of leaf tissues. The activities of peroxidase, ascorbate peroxidase,superoxide dismutase, and glutathione reductase wereobserved to be greater in NaCl-stressed rice leavesthan in control leaves. However, glycolate oxidasewas lower in NaCl-treated rice leaves than in thecontrol leaves. There was no difference in catalaseactivity between NaCl and control treatments. Theseresults suggest that some antioxidant enzymes can beactivated in response to oxidative stress induced byNaCl.     

Photoregulation of morphogenesis of tobacco plants transformed with the gene of human interlenkin-18

The effects of blue light (BL), green light (GL), and red light (RL) on morphogenesis photoregulation of transgenic tobacco (Nicotiana tabacum L.) plants containing a copy of human interleukin-18 gene were studied. Wild-type and transgenic (Il1 No.87–1 and Il18 No.7–11) lines and derived calluses were used. Photomorphogenesis of transgenic lines under GL and RL differed substantially from that of initial line at early stages of morphogenesis; this was expressed in hypocotyl lengthening under GL and cotyledon enhanced expansion under RL. Growth responses to light quality were related to changes in the levels of zeatin, IAA, and ABA. Thus, hypocotyl lengthening and increased cotyledon area under GL occurred at the elevated level of IAA and reduced level of ABA. Growth of callus cells in transgenic lines during zero passage differed from wild-type calluses only in darkness. The data obtained indicate that tobacco plant transformation with the human interleukin-18 gene changed functioning of the photoregulation systems at early developmental stages. This phenomenon is evidently explained by the pleiotropic effects of the gene inserted.     

The role of photorespiration during drought stress: an analysis utilizing barley mutants with reduced activities of photorespiratory enzymes

C _i, intercellular CO₂ concentration
F_v/F_m, quantum efficiency of excitation capture by open photosystem II centres
FBPase, fructose-1,6-bisphosphatase
GAPDH, glyceraldehyde-3-phosphate dehydrogenase
GDC, glycine decarboxylase
GS-2, chloroplastic glutamine synthetase
HPR, hydroxypyruvate reductase
PFD, photon flux density
ΦCO₂, quantum efficiency of CO₂ assimilation
ΦPSII, quantum efficiency of photosystem II electron transport
ψ, water potential
q_N, non-photochemical chlorophyll a fluorescence quenching
q_P, photochemical chlorophyll a fluorescence quenching
RuBP, ribulose-1,5-bisphosphate
Rubisco, ribulose-1,5-bisphosphate carboxylase-oxygenase
SBPase, sedoheptulose-1,7-bisphosphatase
SGAT, serine : glyoxylate aminotransferase

The significance of photorespiration in drought-stressed plants was studied by withholding water from wild-type barley (Hordeum vulgare L.) and from heterozygous mutants with reduced activities of chloroplastic glutamine synthetase (GS-2), glycine decarboxylase (GDC) or serine : glyoxylate aminotransferase (SGAT). Well-watered plants of all four genotypes had identical rates of photosynthesis. Under moderate drought stress (leaf water potentials between –1 and –2 MPa), photosynthesis was lower in the mutants than in the wild type, indicating that photorespiration was increased under these conditions. Analysis of chlorophyll a fluorescence revealed that, in the GDC and SGAT mutants, the lower rates of photosynthesis coincided with a decreased quantum efficiency of photosystem II and increased non-photochemical dissipation of excitation energy. Correspondingly, the de-epoxidation state of xanthophyll-cycle carotenoids was increased several-fold in the drought-stressed GDC and SGAT mutants compared with the wild type. Accumulation of glycine in the GDC mutant was further evidence for increased photorespiration in drought-stressed barley. The effect of drought on the photorespiratory enzymes was determined by immunological detection of protein abundance. While the contents of GS-2 and P- and H-protein of the GDC complex remained unchanged as drought stress developed, the content of NADH-dependent hydroxypyruvate reductase increased. Enzymes of the Benson–Calvin cycle, on the other hand, were either not affected (ribulose-1,5-bisphosphate carboxylase-oxygenase and plastidic fructose-1,6-bisphosphatase) or declined (sedoheptulose- 1,7-bisphosphatase and NADP-dependent glyceraldehyde-3-phosphate dehydrogenase). These data demonstrate that photorespiration was enhanced during drought stress in barley and that the control exerted by photorespiratory enzymes on the rate of photosynthetic electron transport and CO₂ fixation was increased.     

Preferential photoinactivation of catalase and photoinhibition of photosystem II are common early symptoms under various osmotic and chemical stress conditions

Activity of catalase (EC 1.11.1.6) and variable fluorescence (F) were measured in sections of rye leaves (Secale cereale L. cv. Halo) that were exposed for 24 h to moderately high irradiance under osmotic or chemical stress conditions (paraquat, DCMU, mannitol, NaCl, CdCl₂, CuSO₄, Pb(NO₃)₂, KNO₂, or K₂SO₃). Changes of the chlorophyll content and of enzyme activities related to peroxide metabolism, such as glycolate oxidase, glutathione reductase, and peroxidase, were assayed for comparison. In the presence of the herbicides paraquat and low DCMU concentrations that exert only partial inhibition of photosynthesis, as well as after most treatments with osmotic or chemical stress factors, catalase markedly declined due to a preferential photoinactivation. At higher DCMU levels catalase did not decline. At low KNO₂ concentrations catalase activity was preferentially increased. In general, photoinactivation of catalase was accompanied by a decline of the F/F_m ratio, indicating photoinhibition of photosystem II, while other parameters were much more stable. Inasmuch as both catalase and the D1 reaction center protein of photosystem II have a rapid turnover in light, their steady state levels appear to decline whenever stress effects either excessively enhance deleterious oxidative conditions and degradation (e. g. Paraquat, low DCMU), or inhibit repair synthesis. Photoinactivation of catalase and of photosystem II represent specific and widely occurring early symptoms of incipient photodamage indicating stress conditions where the repair capacity is not sufficient. During prolonged exposures, e. g. to NaCl and CuSO₄, chlorophyll was bleached in light and the rate of its photodegradation increased in proportion as the catalase level had declined. The results suggest that the enhanced susceptibility of leaf tissues to photooxidative damage which is widely observed in stressed plants is related to the early loss of catalase.     

Human interferon and cell growth inhibition. III. Separation of activities by treatment with sodium dodecyl sulphate

When human leukocyte interferon was treated with boiling sodium dodecyl sulphate antiviral activity without detectable effect on the growth of human amnion cells could be separated from the growth inhibitory activity by a single gel filtration. Similar results were obtained with mouse L-cell interferon. It is concluded that the two effects of interferon can be separated in distinct molecular entities.     

Alterations of serum selenium, zinc, copper, and iron concentrations and some related antioxidant enzyme activities in patients with cutaneous leishmaniasis

The aim of this study was to measure the alterations in serum selenium (Se), copper (Cu), zinc (Zn), and iron (Fe) concentrations and their carrier proteins, ceruloplasmin (Cp), transferrin (Tf) albumin, and related antioxidant enzyme activities, erythrocyte Cu-Zn Superoxide dismutase (Cu-Zn SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) activities in patients with cutaneous leishmaniasis (CL). Erythrocyte Cu-Zn SOD activities, serum Cu concentrations, and Cp levels were found to be significantly higher in the patients group than those of controls. However, GSH-Px and CAT activities and Se, Zn, Fe, and Tf levels were lower in patients than in the control subjects. There were positive important correlation’s between Cu-Zn SOD and Cp, Cu-Zn SOD and Cu, Cp and Cu, GSH-Px and Se, and Fe and CAT in the patients group. Our results showed that serum essential trace elements Se, Zn, Cu, and Fe concentrations and their related enzymes Cu-Zn SOD, GSH-Px, and CAT activities change in CL patients. The changes may be a part of defense strategies of organism and are induced by the hormonelike substances.     

Blue light-regulation of cell division in Adiantum protonemata: an approach with pulse stimulation

Abstract Cell division of the single-celled Adiantum protonemata produced by red-light (RL) incubation of germinated spores is induced by transfer to darkness and is stimulated by blue light (BL). It is known that the cellular process leading to this cell division includes one cell cycle and the BL response results from shortening of the Gl phase. The authors studied this BL regulation of cell cycle by giving a pulse of BL after RL termination and measuring changes in the proportion of divided cells. To minimize phytochrome responses arising from BL irradiation, the plants were kept in continuous far-red light instead of total darkness after the RL incubation. The response to a pulse (10–100 s) approached saturation with increasing rluences in a manner that reciprocity is valid. The sensitivity to BL, investigated by measuring the response to a saturating pulse, showed an increase in the first several hours after RL termination, followed by a sustained sensitivity for 20 h. Time courses of the pulse-induced responses showed a lag of about 12 h, which was considerably shorter than in the non-stimulated control; the lag was approximately independent of the strength of BL stimulation or the timing of BL application after RL termination, and the major difference occurred in the slope. It is concluded that the sensitivity to BL is retained during the time span in which the dark-dependent Gl phase progresses, and that the BL response is initiated independently of the reactions involved in the dark-dependent Gl phase. A minimal reaction model of Gl phase is suggested to unify the results.     

Treatment with Methyl Jasmonate Alleviates the Effects of Paraquat on Photosynthesis in Barley Plants

Twelve-day-old barley seedlings were supplied with 23 M methyl jasmonate (MeJA) or 10 M paraquat (Pq) via the transpiration stream and kept in the dark for 24 h. Then they were exposed to 100 mol m^–2 s^–1 PAR and samples were taken 1, 2, 3, and 6 h after irradiation. Treatment of seedlings with MeJA alone resulted in decreased content of chlorophyll (Chl), and net photosynthetic (P _N) and transpiration rates. Pq treatment led to a decrease in Chl content and to a very strong inhibition of P _N, the effects were manifested by 1 h of irradiation. Pq treatment did not affect the activity of ribulose-1,5 bisphosphate carboxylase (RuBPC, EC 4.1.1.39) but increased the activity of the photorespiratory enzymes phosphoglycolate phosphatase (PGP, EC 3.1.3.18), glycolate oxidase (GO, EC 1.1.3.1), and catalase (EC 1.11.1.6). Pre-treatment of seedlings with MeJA before exposure to Pq fully blocked the inhibitory effect of Pq on photosynthesis and protected against subsequent Pq-induced oxidative damage.     

二斑叶螨对甲氰菊酯的抗性选育及解毒酶活力变化

为了明确二斑叶螨Tetranychus urticae Koch对甲氰菊酯产生抗性的机理,在室内模拟田间药剂的选择压力, 用甲氰菊酯对二斑叶螨敏感品系（S）进行逐代汰选,选育至38代时, 获得了抗性倍数( resistance ratio, RR)为247.35的抗甲氰菊酯品系（Fe-R）。对S和Fe-R解毒酶活性的分析表明,Fe-R₃₈体内羧酸酯酶（carboxylesterase, CarE）、酸性磷酸酯酶(acid phosphatase, ACP)、 碱性磷酸酯酶(alkaline phosphatase, ALP)、谷胱甘肽-S-转移酶(glutathione s-transferase, GSTs)和多功能氧化酶(mixed function oxidase, MFO)较S体内相应酶的活力显著升高（P< 0.05）,其相对比值（R/S）分别为1.822,13.941,3.789,4.262和17.386。此外,筛选至第9,19,25,32代时,除Fe-R₂₅和Fe-R₃₂的MFO活性与S相比有显著性差异（P< 0.05）外,其余解毒酶（CarE,ACP,ALP,GSTs）的活性与S相比均无显著性差异(P>0.05)。筛选至第38代时, 5种解毒酶的活力与S相比均差异显著(P<0.05)。结果说明二斑叶螨Fe-R随着筛选代数的增加（第25代后）,MFO活性的上升可能是二斑叶螨对甲氰菊酯产生抗性的主要原因。     

Changes of net photosynthesis,antioxidant enzyme activities,and antioxidant contents of <Emphasis Type="Italic">Liriodendron tulipifera</Emphasis> under elevated ozone

Liriodendron tulipifera was exposed to gradually elevated ozone concentrations of 100–300 μg kg⁻¹ in the naturally irradiated environment chamber. During 15 d of exposure to O₃, net photosynthetic rate (P _N) decreased and there was large difference between the control (C) and treatment with ozone (OT), while there was no significant difference in water use efficiency. Total chlorophyll content as well as the value of fluorescence parameter F_v/F_m decreased, while antioxidant enzyme activities related to ascorbate-glutathione cycle increased after 15 d of OT. Unchanged contents of ascorbate and glutathione indirectly suggest that the species hastened the antioxidant’s oxidization/reduction cycle using enzymes instead of expanding their pool against oxidative stress.     

Correlation of seasonal acclimatization in metabolic enzyme activity with preferred body temperature in the Eastern red spotted newt (Notophthalmus viridescens viridescens)

Eastern red spotted newts, as aquatic adults, are active year round. They are small and easy to handle, and thus lent themselves to a laboratory study of seasonal changes in preferred body temperature and biochemical acclimatization. We collected newts in summer (n=20), late fall (n=10) and winter (n=5). Ten each of the summer and late fall newts were subjected to an aquatic thermal gradient. Summer newts maintained higher cloacal temperatures than late fall newts (26.8+/-0.5 degrees C and 17.2+/-0.4 degrees C, respectively). In addition, the activity of three muscle metabolic enzymes (cytochrome c oxidase (CCO), citrate synthase (CS) and lactate dehydrogenase (LDH)) was studied in all newts collected. Newts compensated for lower late fall and winter temperatures by increasing the activity of CCO during those seasons over that in summer newts at all assay temperatures (8, 16 and 26 degrees C). The activity of CS was greater in winter over summer newts at 8 and 16 degrees C. No seasonal differences in LDH activity were demonstrated. These data in newts indicate that this amphibian modifies some muscle metabolic enzymes in relation to seasonal changes and can modify its behavioral in a way that correlates with those biochemical changes.