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1.
In C4 plants phosphoenolpyruvate (PEP) of the C4 cycle may betransported on a chloroplast transporter which also transports3-phosphoglycerate (3-PGA) and triosephosphates. In C3 plantsPEP is not considered to be effectively transported on the chloroplastphosphate translocator. The influences of certain organic phosphates,having a similar structure to either PEP or triose-phosphates,on 3-PGA dependent O2 evolution by C4 (Digitaria sanquinalisL. Scop.) and C3 (Hordeum vulgare L.) mesophyll chloroplastswere investigated. In the C4 mesophyll chloroplasts phosphoglycolatewas a competitive inhibitor (Ki = 2.1 mM) of 3-PGA dependentO2 evolution, and was as effective as previously reported forPEP. 2-Phosphoglycerate was also a competitive inhibitor (Kt= 8.6 mM) of O2 evolution in the C4 mesophyll chloroplasts with3-PGA as substrate, while phospholactate was a weak inhibitorand glyphosate had no effect. Neither PEP, phosphoglycolatenor 2-phosphoglycerate were effective inhibitors of 3- PGA dependentO2 evolution in the C3 chloroplasts. Phosphohydroxypyruvatewas a competitive inhibitor of 3-PGA dependent O22 evolutionin both chloroplast types. The selectivity in inhibition ofO2 evolution with 3-PGA as substrate suggests that the C4 mesophyllchloroplasts can recognize certain organic phosphates with thephosphate in the C-2 or C-3 position but that the C4 mesophyllchloroplasts can only effectively recognize certain organicphosphates with the phosphate in the C-3 position. The resultsalso support the view that 3-PGA and PEP are transported onthe same phosphate translocator in C4 mesophyll chloroplasts.
1 Current address: Department of Horticulture, 2001 Fyffe Court,The Ohio State University, Columbus, Ohio 43210-1096. (Received March 24, 1987; Accepted April 16, 1987) 相似文献
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Theo J. Visser Ellen Van Overmeeren-Kaptein 《Biochimica et Biophysica Acta (BBA)/General Subjects》1980,631(2):246-252
A radioimmunoassay for 3′-iodothyronine has been developed. All iodothyronine analogues (except 3,3′-diiodothyronine) showed very little (0.02% at most) cross-reactivity, and the assay was sensitive to 1 pg 3′-iodothyronine/ tube. We have studied the 5′-deiodination of 3′,5′-diiodothyronine by rat liver microsomal fraction in the presence of dithiothreitol. Production of 3′-iodothyronine at 37°C was found to be linear with time of incubation up to 30 min and with concentration of microsomal protein up to 100 μg/ml. The reaction rate reached a limit on increasing 3′,5′-diiodothyronine concentration to 10 μM. The effect of pH on 3′-iodothyronine production was found to depend on 3′,5′-diiodothyronine concentration. Increasing 3′,5′-diiodothyronine concentration from 0.1 to 10 μM resulted in a shift of the pH optimum from 6–6.5 to 7.5. Similar effects on the 5′-deiodination of 3,3′,5′-triiodothyronine were observed, supporting the hypothesis that these reactions are catalysed by a single enzyme (iodothyronine 5′-deiodinase). 相似文献
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Butow Barbara; Wynne David; Sukenik Assaf; Hadas Ora; Tel-Or Elisha 《Journal of plankton research》1998,20(2):355-369
Lipid peroxidation in Peridinium samples taken from two differentdepths in Lake Kinneret fluctuated throughout the spring withan overall increasing trend. Samples from 0.5 and 5 m showeda similar peroxidation pattern, which was maximal after thefall off in algal biomass. The rapid decline in Peridinium biomasscoincided with ambient lake temperatures of 2123C. Fattyacid composition profiles were similar at both depths, althoughafter the peak of the bloom, a significant increase in polyunsaturatedfatty acids and oleic acid was only found at 0.5 m, togetherwith a decrease in the percentage of polyunsaturated fatty acids.These effects were related to ambient light stress rather thana result of lipid peroxidation. Lake samples taken at differentperiods of the bloom and incubated at various temperatures showeddifferential peroxidation. Higher temperatures caused increasedlipid peroxidation, but this appeared to be dependent on thesampling period. Samples withdrawn from the lake at the beginningof the bloom showed little peroxidation after a 5 day incubationat 14C, room temperature (25C) or ambient lake temperature(16C) compared to mid-bloom samples in which there was a significantincrease in peroxidation when they were incubated at room temperature(25C) or ambient lake temperature (22C). Incubation at 14Cinhibited peroxidation; however, samples from mid-bloom againshowed enhanced peroxidation compared with those from the beginningof the bloom. These in situ results suggested a relationshipbetween temperature, another environmental variable during thebloom and lipid peroxidation in Peridinium. As total dissolvedinorganic carbon (DIC) concentrations fall significantly duringthe progress of the bloom and represent an important sourceof environmental stress, laboratory experiments were establishedto investigate the synergistic effect of temperature and carbonnutrition on lipid peroxidation in Peridinium cultures. Increasedtemperature alone caused a slight increase in lipid peroxidation,but this was greatly augmented by carbon limitation. Althoughcarbon limitation induced increased catalase activity, at highertemperatures activity declined after 48 h, allowing for thesubstantial increase in lipid peroxidation. 相似文献
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Kathryn S. Evans Janneke Wit Lewis Stevens Steffen R. Hahnel Briana Rodriguez Grace Park Mostafa Zamanian Shannon C. Brady Ellen Chao Katherine Introcaso Robyn E. Tanny Erik C. Andersen 《PLoS pathogens》2021,17(3)
Parasitic nematodes cause a massive worldwide burden on human health along with a loss of livestock and agriculture productivity. Anthelmintics have been widely successful in treating parasitic nematodes. However, resistance is increasing, and little is known about the molecular and genetic causes of resistance for most of these drugs. The free-living roundworm Caenorhabditis elegans provides a tractable model to identify genes that underlie resistance. Unlike parasitic nematodes, C. elegans is easy to maintain in the laboratory, has a complete and well annotated genome, and has many genetic tools. Using a combination of wild isolates and a panel of recombinant inbred lines constructed from crosses of two genetically and phenotypically divergent strains, we identified three genomic regions on chromosome V that underlie natural differences in response to the macrocyclic lactone (ML) abamectin. One locus was identified previously and encodes an alpha subunit of a glutamate-gated chloride channel (glc-1). Here, we validate and narrow two novel loci using near-isogenic lines. Additionally, we generate a list of prioritized candidate genes identified in C. elegans and in the parasite Haemonchus contortus by comparison of ML resistance loci. These genes could represent previously unidentified resistance genes shared across nematode species and should be evaluated in the future. Our work highlights the advantages of using C. elegans as a model to better understand ML resistance in parasitic nematodes. 相似文献
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T. G. Wynne Parry 《BMJ (Clinical research ed.)》1939,2(4102):396-397
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The growth (fresh and dry weight increase) of potato tuber ( Solanum tuberosum L. cv. Bintje) callus discs was stimulated by incubation in air with 500 ppm 2,5-norbornadiene (NBD, a competitive inhibitor of ethylene action) and inhibited by incubation in air with 4 000 ppm NBD. Ethylene formation by the callus was stimulated by NBD. The development of the alternative pathway, measured in isolated mitochondria was inhibited by NBD in a concentration-dependent way. The alternative pathway capacity, measured in vivo, was inhibited by 4 000 ppm NBD, but not by 500 ppm. Uninhibited in vivo respiration, which consists of cytochrome path activity and alternative path activity, was stimulated by the treatment with 500 ppm NBD. The main contribution to this stimulation was made by the cytochrome pathway. In 4 000 ppm NBD-treated callus, uninhibited respiration seemed to be unaffected as a consequence of an inhibited cytochrome path activity, which was compensated by a stimulated alternative path activity. Both in 500 and 4 OIK) ppm NBD-treated callus the alternative path activity in vivo was stimulated.
The regulatory role for endogenous ethylene in potato tuber callus is discussed in relation to: 1) The induction of respiratory pathways, 2) the supply of reduction equivalents in vivo and 3) growth. 相似文献
The regulatory role for endogenous ethylene in potato tuber callus is discussed in relation to: 1) The induction of respiratory pathways, 2) the supply of reduction equivalents in vivo and 3) growth. 相似文献