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1.
Nature, intracellular distribution and formation of terpenoid quinones in maize and barley shoots 总被引:7,自引:7,他引:0
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1. Maize and barley shoots have been shown to contain phylloquinone, plastoquinone, α-tocopherol (and γ-tocopherol in maize), α-tocopherolquinone and ubiquinone-9. 2. No solanesol was detected in any tissue examined. 3. In maize shoots plastoquinone and α-tocopherolquinone were localized in the chloroplast; ubiquinone was in the mitochondria. 4. Etiolated (dark-grown) shoots contained smaller amounts of phylloquinone and plastoquinone; α-tocopherolquinone was entirely absent; ubiquinone and α-tocopherol concentrations were unaffected. 5. On illumination of etiolated shoots the chloroplastidic quinones phylloquinone, plastoquinone and α-tocopherolquinone were synthesized in step with chloroplast development. α-Tocopherolquinone was not formed at the immediate expense of α-tocopherol. 相似文献
2.
1. 26-Hydroxycholesterol was obtained by reducing the methyl ester of (±)-3β-hydroxycholest-5-en-26-oic acid, which was synthesized from 25-oxonorcholesterol. 2. Methods for preparing 7α-hydroxycholesterol and 7-dehydrocholesterol were modified to allow the micro-scale preparation of these [14C]sterols from [26-14C]-cholesterol. 3. 26-Hydroxycholesterol was oxidized more readily than 7α-hydroxycholesterol, 7-dehydrocholesterol or cholesterol by mitochondrial preparations from livers of mice, rats, guinea pigs, common toads (Bufo vulgaris) and Caiman crocodylus. 4. (±)-3β-Hydroxy[26-14C]cholest-5-en-26-oic acid was oxidized very rapidly to 14CO2 by mouse and guinea-pig mitochondria without evident discrimination between the two optical isomers. 5. An enzyme system that oxidizes 26-hydroxycholesterol to 3β-hydroxycholest-5-en-26-oic acid was identified in the soluble extract of rat-liver mitochondria. This enzyme could use NADP in place of NAD but was not identical with liver alcohol dehydrogenase (EC 1.1.1.1). 6. [26-14C]Cholesteryl 3β-sulphate was not oxidized by fortified mouse-liver preparations that oxidized [26-14C]cholesterol to 14CO2. 相似文献
3.
Metabolism of Radiolabeled β-Guaiacyl Ether-Linked Lignin Dimeric Compounds by Phanerochaete chrysosporium
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David A. Weinstein Kanit Krisnangkura Mary B. Mayfield Michael H. Gold 《Applied microbiology》1980,39(3):535-540
Phanerochaete chrysosporium metabolized the radiolabeled lignin model compounds [γ-14C]guaiacylglycerol-β-guaiacyl ether and [4-methoxy-14C]veratrylglycerol-β-guaiacyl ether (VI) to 14CO2 in stationary and in shaking cultures. 14CO2 evolution was greater in stationary culture. 14CO2 evolution from [γ-14C]guaiacyl-glycerol-β-guaiacyl ether and [4-methoxy-14C]veratrylglycerol-β-guaiacyl ether in stationary cultures was two- to threefold greater when 100% O2 rather than air (21% O2) was the gas phase above the cultures. 14CO2 evolution from the metabolism of the substrates occurred only as the culture entered the stationary phase of growth. The presence of substrate levels of nitrogen in the medium suppressed 14CO2 evolution from both substrates in stationary cultures. [14C]veratryl alcohol and 4-ethoxy-3-methoxybenzyl alcohol were formed as products of the metabolism of VI and 4-ethoxy-3-methoxyphenylglycerol-β-guaiacyl ether, respectively. 相似文献
4.
Jill E. Cremer 《The Biochemical journal》1967,104(1):212-222
1. The rate of appearance of 14CO2 from [6-14C]glucose and [3-14C]pyruvate was measured. Pyruvate is oxidized to carbon dioxide twice as fast as glucose, although the oxygen uptake is almost the same with each substrate. 2. The presence of 30μm-2,4-dinitrophenol increases the output of 14CO2 from [6-14C]glucose sixfold whereas the oxygen uptake is not quite doubled. Similar results are obtained with 0·1m-potassium chloride. The stimulating action of these two agents on the output of 14CO2 from [3-14C]pyruvate is much less than on that from [6-14C]glucose. 3. The effects of oligomycin, ouabain and triethyltin on the respiration of control and stimulated brain-cortex slices were studied. Triethyltin (1·3μm) inhibited the oxidation of [6-14C]glucose more than 70%, but did not inhibit the oxidation of[3-14C]pyruvate. [3-14C]pyruvate. 4. The production of lactic acid by brain-cortex slices incubated with glucose is twice as great as that with pyruvate. Lactic acid increases two and a half times in the presence of either triethyltin or oligomycin when the substrate is glucose, but is no different from the control when the substrate is pyruvate. 5. With kidney slices the production of lactic acid from glucose is very low. It is increased by oligomycin but not by triethyltin. 6. The results are discussed in terms of the oxidation of the extramitochondrial NADH2 produced during glycolysis. 相似文献
5.
1. 2-Methyl[1-14C]octanoic acid was synthesized from 2-bromo-octane and 14CO2. 2. 2-Methyl[1-14C]octanoic acid was readily oxidized to propionic acid and carbon dioxide by mitochondrial preparations from liver, less readily oxidized by adrenal and kidney (mitochondria), and only poorly oxidized by heart, spleen and brown fat (mitochondria). 3. 3β-Hydroxy[26-14C]cholest-5-en-26-oic acid was rapidly oxidized by mammalian-liver mitochondria to propionic acid and carbon dioxide. Caiman-liver and toad-liver mitochondria also oxidized this steroid acid. 4. The oxidation of propionic acid, octanoic acid and palmitic acid by mitochondrial preparations from these various tissues was also studied. 5. Added carnitine did not stimulate 2-methyloctanoic acid oxidation and feebly stimulated 3β-hydroxycholest-5-en-26-oic acid oxidation. 6. The significance of these results is discussed in relation to sterol catabolism in mammals and non-mammalian species. 相似文献
6.
In various cellular subfractions of Calendula officinalis leaves a study was made of the distribution of polyprenyl quinones and α-tocopherol and the dynamics of their labelling with 14CO2 and acetate-[1-14C] and incorporation of mevalonate-[2-14C] after 3 hr. It was confirmed that plastoquinone occurs only in the chloroplasts, ubiquinone only in the mitochondria and α-tocopherol in both these subfractions. Phylloquinone was found in the chloroplast and mitochondrial fractions as well as in the post-mitochondrial supernatant. Studies of the dynamics of radioactive precursor incorporation indicated that α-tocopherol is metabolized more rapidly than the polyprenyl quinones studied; the incorporation of mevalonate-[2-14C] suggests that the side chain of plastoquinone can be synthesized in the cytoplasm and transported to the chloroplasts. 相似文献
7.
Incorporation and Degradation of C and H-labeled Thymidine by Sugarcane Cells in Suspension Culture 总被引:2,自引:0,他引:2
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Lesley SM 《Plant physiology》1980,65(6):1224-1228
Sugarcane cells growing in suspension culture degrade exogenous thymidine, releasing thymine. Thymine is not utilized for DNA synthesis. Thymine is rapidly catabolized to β-aminoisobutyric acid which is found within the cell. Thymidine in the medium is used for DNA synthesis. The label of [2-14C]thymidine is lost as 14CO2, but the label of [3H]methylthymidine is found in the cell as [3H]β-aminoisobutyric acid, some of which is used for the synthesis of other cell components. The degradation of thymidine can be partially inhibited by addition of certain substituted pyrimidines. 相似文献
8.
1. Experiments were performed to throw light on why the incorporation of 14C from labelled carbohydrate precursors into glutamate has been found to be more marked in brain than in other tissues. 2. Rapid isotope exchange between labelled glutamate and unlabelled α-oxoglutarate was demonstrated in brain and liver mitochondrial preparations. In the presence but not in the absence of α-oxoglutarate the yield of 14CO2 from [1-14C]glutamate exceeded the net glutamate removal, and the final relative specific activities of the two substrates indicated that complete isotopic equilibration had occurred. Also, when in a brain preparation net glutamate removal was inhibited by malonate, isotope exchange between [1-14C]glutamate and α-oxoglutarate and the formation of 14CO2 were unaffected. 3. The time-course of isotope exchange between labelled glutamate and unlabelled α-oxoglutarate was followed in uncoupled brain and liver mitochondrial fractions, and the rate of exchange calculated by a computer was found to be 3–8 times more rapid than the maximal rate of utilization of the two substrates. 4. The physiological situation was imitated by the continuous infusion of small amounts of α-oxo[1-14C]glutarate into brain homogenate containing added glutamate. The fraction of 14C infused that was retained in the glutamate pool depended on the size of the latter, and the final relative specific activities of the two substrates indicated almost complete isotope exchange. Isotopic equilibration also occurred when α-oxoglutarate was generated from pyruvate through the tricarboxylic acid cycle in a brain mitochondrial preparation containing [1-14C]glutamate. 5. The differences in the incorporation of 14C from labelled glucose into the glutamate of brain and liver are discussed in terms of the rates of isotope exchange, the glutamate pool sizes and the rates of formation of labelled α-oxoglutarate in the two tissues. It is concluded that the differences between tissues in the incorporation of glucose carbon into glutamate reflect features of their metabolism largely unrelated to that of glutamate. 相似文献
9.
Lawrence J. Marnett Joseph Buck Melissa A. Tuttle Ashis K. Basu Arthur W. Bull 《Prostaglandins & other lipid mediators》1985,30(2):241-254
The
metabolism of melondialdehyde (MDA) by male and female Swiss mice was investigated. Distribution of an i.p. dose of MDA is rapid and uniform throughout the body. Conversion of 14C-labeled MDA to CO2 is complete 4 hours after an i.p. dose of 5 μmol to 200 μmol with no signs of short term toxicity. The yields of CO2 from [1-14C]-β-alanine, [3-14C]-β-alanine, [1-14C]-sodium acetate, and [2-14C]-sodium acetate were also determined. Comparison of the yields of CO2 from this series of compounds suggests the intermediacy of malonic semialdehyde in the metabolism of MDA. High doses (600 μmol) of β-alanine or acetate given prior to 14C-MDA reduced the yield of 14CO2. Ethanol and disulfiram were both inhibitors of MDA metabolism, indicating the involvement of aldehyde dehydrogenase in the oxidation of MDA.These data demonstrate the ability of animal tissues to rapidly remove exogeneously administered MDA. They also have implications with respect to the possible pathological consequences of
MDA generation. 相似文献
10.
Metabolism of surfactants sodium undecyltriethoxy sulphate and sodium dodecyltriethoxy sulphate in the rat
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Andrew J. Taylor Gillian M. Powell Douglas Howes J. Gordon Black Anthony H. Olavesen 《The Biochemical journal》1978,174(2):405-412
The metabolic fates of the synthetic surfactants, sodium [1-14C]undecyltriethoxy sulphate and sodium [1-14C]dodecyltriethoxy sulphate were studied in the rat. Both compounds were extensively metabolized regardless of the route of administration, oral, intraperitoneal or intravenous. Short-chain radioactive products were eliminated in the urine: the major metabolite of the dodecyl homologue in the urine was identified as −O2C14CH2- (OC2H4)3OSO3− by n.m.r. and g.l.c.–mass spectrometry, whereas the major metabolite of the undecyl homologue in the urine was tentatively identified as −O2CCH214CH2- (OC2H4)3OSO3−. In contrast with experiments with the dodecyl derivative, when [1-14C]undecyltriethoxy sulphate was administered to rats, appreciable amounts of radioactivity were recovered as 14CO2 in expired air. Whole-body radioautography implicated the liver as the major site of metabolism of both surfactants. The nature of the metabolic products establishes that both compounds are degraded by ω,β-oxidation. Cleavage of the ether linkage proximal to the sulphate moiety may account for the small amounts of 14CO2 recovered in expired air after the administration of [1-14C]dodecyltriethoxy sulphate. It is suggested the substantial amounts of 14CO2 recovered after [1-14C]-undecyltriethoxy sulphate administration originate from −O214C(OC2H4)3 OSO3−, an unstable product of ω,β-oxidation. An n.m.r. spectrum of the metabolite identified as 2-(triethoxy sulphate)acetic acid and a mass spectrum of the trimethylsilyl derivative of the parent alcohol of that metabolite have been deposited as Supplementary Publication SUP50086 (5 pages) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1978) 169, 5. 相似文献
11.
Metabolism of Acetate, Methanol, and Methylated Amines in Intertidal Sediments of Lowes Cove, Maine 总被引:14,自引:11,他引:3
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The fates and the rates of metabolism of acetate, trimethylamine, methylamine, and methanol were examined to determine the significance of these compounds as in situ methane precursors in surface sediments of an intertidal zone in Maine. Concentrations of these potential methane precursors were generally <3 μM, with the exception of sediments containing fragments of the seaweed Ascophyllum nodosum, in which acetate was 96 μM. [2-14C]acetate turnover in all samples was rapid (turnover time <2 h), with 14CO2 as the primary product. [14C]trimethylamine and methylamine turnover times were slower (>8 h) and were characterized by formation of both 14CH4 and 14CO2. Ratios of 14CH4/14CO2 from [14C]trimethylamine and methylamine in uninhibited sediments indicated that a significant fraction of these substrates were catabolized via a non-methanogenic process. Data from inhibition experiments involving sodium molybdate and 2-bromoethanesulfonic acid supported this interpretation. [14C]methanol was oxidized relatively slowly compared with the other substrates and was catabolized mainly to 14CO2. Results from experiments with molybdate and 2-bromoethanesulfonic acid suggested that methanol was oxidized primarily through sulfate reduction. In Lowes Cove sediments, trimethylamine accounted for 35.1 to 61.1% of total methane production. 相似文献
12.
beta-Carotene Synthesis in Isolated Spinach Chloroplasts : Its Tight Linkage to Photosynthetic Carbon Metabolism
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Carefully isolated intact spinach chloroplasts virtually free of contamination of other organelles effectively form β-carotene from NaH14CO3 or [U-14C]-3-phosphoglycerate (PGA) under photosynthetic conditions. The photosynthate pool formed in chloroplasts from 1 to 2 millimolar [U-14C]-3-PGA or 3 to 6 millimolar NaH14CO3 was fully sufficient to supply β-carotene synthesis with intermediates for about 1 hour at maximal rates of about 20 nanomoles 14C incorporated per milligram chlorophyll per hour. Fatty acid synthesis remains, under these circumstances, in linear dependence to substrate concentrations with far lower activity. Isotopic dilution of the β-carotene synthesis by adding unlabeled glyceraldehyde 3-phosphate, dihydroxyacetone-P, 3-PGA, 2-PGA, phosphoenolpyruvate, pyruvate, respectively, may be interpreted as a direct substrate flow from photosynthetically fixed CO2 to isopentenyl pyrophosphate synthesizing system. Unlabeled acetate did not dilute β-carotene synthesis. Fatty acid synthesis acted similarly with unlabeled substrates; but it also was diluted by unlabeled acetate. These results indicate a tight linkage of photosynthetic carbon fixation and plastid isoprenoid synthesis. 相似文献
13.
Metabolism of Linoleic Acid or Mevalonate and 6-Pentyl-α-Pyrone Biosynthesis by Trichoderma Species
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The understanding of the biosynthetic pathway of 6-pentyl-α-pyrone in Trichoderma species was achieved by using labelled linoleic acid or mevalonate as a tracer. Incubation of growing cultures of Trichoderma harzianum and T. viride with [U-14C]linoleic acid or [5-14C]sodium mevalonate revealed that both fungal strains were able to incorporate these labelled compounds (50 and 15%, respectively). Most intracellular radioactivity was found in the neutral lipid fraction. At the initial time of incubation, the radioactivity from [14C]linoleic acid was incorporated into 6-pentyl-α-pyrone more rapidly than that from [14C]mevalonate. No radioactivity incorporation was detected in 6-pentyl-α-pyrone when fungal cultures were incubated with [1-14C]linoleic acid. These results suggested that β-oxidation of linoleic acid was a probable main step in the biosynthetic pathway of 6-pentyl-α-pyrone in Trichoderma species. 相似文献
14.
Abscisic Acid Metabolism in Salt-Stressed Cells of Dunaliella salina: Possible Interrelationship with beta-Carotene Accumulation
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The interrelationship between abscisic acid (ABA) production and β-carotene accumulation was investigated in salt-stressed cells of the halotolerant green alga Dunaliella salina var bardawil. Cells were supplied with either R-[2-14C]mevalonolactone or [14C] sodium bicarbonate for 20 hours and then exposed to increased salinity (1.5 to 3.0 molar NaCl) for various lengths of time. Incorporation of label into abscisic acid and phaseic acid and the distribution of [14C]ABA between the cells and incubation media were monitored. [14C]ABA and [14C]phaseic acid were identified as products of both R-[2-14C]mevalonolactone and [14C]sodium bicarbonate metabolism. ABA metabolism was enhanced by hypersalinity stress. Actinomycin D, chloramphenicol, and cycloheximide abolished the stress-induced production of ABA, suggesting a role for gene activation in the process. Kinetic analysis of both ABA and β-carotene production demonstrated two stages of accelerated β-carotene production. In addition, ABA levels increased rapidly, and this increase occurred coincident with the early period of accelerated β-carotene production. A possible role for ABA as a regulator of carotenogenesis in cells of D. salina is therefore discussed. 相似文献
15.
The effects of levulinic Acid and 4,6-dioxoheptanoic Acid on the metabolism of etiolated and greening barley leaves 总被引:5,自引:5,他引:0
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Application of levulinic acid (LA), a competitive inhibitor of δ-aminolevulinic acid (ALA) dehydratase, to greening plant tissues causes ALA to accumulate at the expense of chlorophyll. 4,6-Dioxoheptanoic acid (DA), which has been reported to be an effective inhibitor of this enzyme in animal systems, has a similar but more powerful effect on ALA and chlorophyll metabolism in greening leaves of Hordeum vulgare L. var. Larker. Both LA and DA also inhibit the uptake of [14C]amino acids into etiolated and greening barley leaves and reduce their incorporation into protein. Treatment of etiolated and greening leaves with these compounds results in the inhibition of 14CO2 evolution from labeled precursors, including amino and organic acids. Inhibition of 14CO2 evolution by these compounds is more effective in greening leaves than in etiolated leaves when [4-14C]ALA or [1-14C]glutamate are employed as precursors. Both LA and DA also inhibit the uptake and increase the incorporation of 32Pi into organophosphorus by etiolated barley leaves. These results indicate that LA and DA have more far-reaching effects upon plant metabolism than was previously believed. 相似文献
16.
Biochemistry of Suberization: Incorporation of [1-C]Oleic Acid and [1-C]Acetate into the Aliphatic Components of Suberin in Potato Tuber Disks (Solanum tuberosum)
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Biosynthesis of the aliphatic components of suberin was studied in suberizing potato (Solanum tuberosum) slices with [1-14C]oleic acid and [1-14C]acetate as precursors. In 4-day aged tissue, [1-14C]oleic acid was incorporated into an insoluble residue, which, upon hydrogenolysis (LiA1H4), released the label into chloroform-soluble products. Radio thin layer and gas chromatographic analyses of these products showed that 14C was contained exclusively in octadecenol and octadecene-1, 18-diol. OsO4 treatment and periodate cleavage of the resulting tetraol showed that the labeled diol was octadec-9-ene-1, 18-diol, the product expected from the two major components of suberin, namely 18-hydroxyoleic acid and the corresponding dicarboxylic acid. Aged potato slices also incorporated [1-14C]acetate into an insoluble material. Hydrogenolysis followed by radio chromatographic analyses of the products showed that 14C was contained in alkanols and alkane-α,ω-diols. In the former fraction, a substantial proportion of the label was contained in aliphatic chains longer than C20, which are known to be common constituents of suberin. In the labeled diol fraction, the major component was octadec-9-ene-1,18-diol, with smaller quantities of saturated C16, C18, C20, C22, and C24-α,ω-diols. Soluble lipids derived from [1-14C]acetate in the aged tissue also contained labeled very long acids from C20 to C28, as well as C22 and C24 alcohols, but no labeled ω-hydroxy acids or dicarboxylic acids were detected. Label was also found in n-alkanes isolated from the soluble lipids, and the distribution of label among them was consistent with the composition of n-alkanes found in the wound periderm of this tissue; C21 and C23 were the major components with lesser amounts of C19 and C25. The amount of 14C incorporated into these bifunctional monomers in 0-, 2-, 4-, 6-, and 8-day aged tissue were 0, 1.5, 2.5, 0.8, and 0.3% of the applied [1-14C]oleic acid, respectively. Incorporation of [1-14C]acetate into the insoluble residue was low up to the 3rd day of aging, rapid during the next 4 days of aging, and subsequently the rate decreased. These changes in the rates of incorporation of exogenous oleic acid and acetate reflected the development of diffusion resistance of the tissue surface to water vapor. As the tissue aged, increasing amounts of the [1-14C]acetate were incorporated into longer aliphatic chains of the residue and the soluble lipids, but no changes in the distribution of radioactivity among the α-ω-diols were obvious. The above results demonstrated that aging potato slices constitute a convenient system with which to study the biochemistry of suberization. 相似文献
17.
An investigation into the role of malonyl-coenzyme A in isoprenoid biosynthesis 总被引:4,自引:3,他引:1
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1. [14C]Malonyl-CoA was incorporated into isoprenoids by cell-free yeast preparations, by preparations from pigeon and rat liver, and by Hevea brasiliensis latex. 2. In agreement with previous reports the incorporation of acetyl-CoA into isoprenoids was not inhibited by avidin and was not stimulated by HCO3−. In a cell-free yeast preparation addition of HCO3− stimulated the formation of fatty acids from acetyl-CoA and decreased the incorporation into unsaponifiable lipids. 3. The labelling patterns of β-hydroxy-β-methylglutaryl-CoA formed from [2-14C]- and [1,3-14C]-malonyl-CoA in rat and pigeon liver preparations were those that would be expected if malonyl-CoA underwent decarboxylation to acetyl-CoA before incorporation. 4. The labelling pattern of ergosterol formed by cell-free yeast preparations from [2-14C]malonyl-CoA was also consistent with decarboxylation of malonyl-CoA before incorporation. 5. The incorporation of [2-14C]malonyl-CoA into mevalonate by rat liver preparations was related to the malonyl-CoA decarboxylase activity present in the preparation. 相似文献
18.
Wood-grown cultures of Daldinia concentrica oxidized a permethylated β-14C-labeled synthetic lignin to 14CO2 and also cleaved a permethylated α-13C-labeled synthetic lignin to give Cα-Cβ cleavage products that were detected by 13C nuclear magnetic resonance spectrometry. Therefore, this ascomycete resembles white-rot basidiomycetes in attacking the recalcitrant nonphenolic structures that predominate in lignin. 相似文献
19.
Particulate enzyme preparations from Phaseolus aureus hypocotyls catalyze the formation of an alkali insoluble β, 1 → 4 linked [14C]-glucan using UDP-α-d [14C]-glucose as substrate. Particulate enzymes prepared from root tissue also catalyzed the production of β, 1 → 4 glucan. UDP-β-d-[14C]-glucose would not serve as a substrate for these enzymes. The presence or absence of β, 1 → 4 glucan synthetase activity was independent of tissue source, substrate concentration, or homogenization method. 相似文献
20.
Microbial reductive dechlorination of [1,2-14C]trichloroethene to [14C]cis-dichloroethene and [14C]vinyl chloride was observed at 4°C in anoxic microcosms prepared with cold temperature-adapted aquifer and river sediments from Alaska. Microbial anaerobic oxidation of [1,2-14C]cis-dichloroethene and [1,2-14C]vinyl chloride to 14CO2 also was observed under these conditions. 相似文献