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1.
Convallaria majalis plants were fed dl-methionine-[1-14C]. [1-14C, 4-3H], and [1-14C, 2-3H], S-adenosyl-l-methionine-[1-14C], and dl-homoserine-[1-14C], resulting in the formation of labeled azetidine-2-carboxylic acid (A-2-C). The complete retention of tritium relative to carbon-14 in the feeding experiment involving methionine-[1-14C, 4-3H] indicates that aspartic acid or aspartic-β-semialdehyde are not intermediates between methionine and A-2-C. However, since the A-2-C derived from methionine-[1-14C, 2-3H] had lost 95% of the tritium relative to the C-14, it is not considered that methionine or its S-adenosyl derivative are the immediate precursors of A-2-C. Our data and that of others is consistent with the intermediate formation of γ-amino-α-ketobutyric acid which on cyclization yields 1-azetine-2-carboxylic acid, A-2-C then being formed on reduction. 相似文献
2.
The Biosynthesis of Some Isothiocyanates and Oxazolidinethiones in Rape (Brassica campestris L.)
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The incorporation of the radioactivity from acetate-1-14C, acetate-2-14C, dl-methionine-1-14C, dl-methionine-2-14C, dl-methionine-3,4-14C, dl-homomethionine-2-14C, dl-allyl-glycine-2-14C, and dl-2-amino-5-hydroxyvalerate-2-14C into the aglycones of progoitrin, gluconapin, and glucobrassicanapin of maturing rape plants (Brassica campestris L.) was investigated. Radioactivity from dl-methionine-2-14C, dl-methionine-3,4-14C, dl-homomethionine-2-14C, and acetate-2-14C were incorporated into the 3 major thioglucosides. The other organic compounds were poorly incorporated except for dl-allylglycine-2-14C into glucobrassicanapin. The results obtained suggest that the rape plant can synthesize amino acids by the condensation of acetate (as acetyl CoA) to α-keto acids to yield a homologue of the original amino acid. These newly formed amino acids are then employed to synthesize the 3 major thioglucosides. 相似文献
3.
Glaser V. M. Al-Nuri M. A. Groshev V. V. Shestakov S. V. 《Archives of microbiology》1973,92(3):217-226
Summary The labelling of nucleic acids of growing cells of the blue-green algae Anacystis nidulans and Synechocystis aquatilis by radioactive precursors has been studies. A. nidulans cells most actively incorporate radioactivity from [2-14C]uracil into both RNA and DNA, while S. aquatilis cells incorporate most effectively [2-14C]uracil and [2-14C]thymine.Deoxyadenosine does not affect incorporation of label from [2-14C]thymidine into DNA, but weakly inhibits [2-14C]thymine incorporation into both nucleic acids and significantly suppresses the incorporation of [2-14C]uracil.The radioactivity from [2-14C]uracil and [2-14C]thymine is found in RNA uracil and cytosine and DNA thymine and cytosine. The radioactivity of [2-14C]thymidine is incorporated into DNA thymine and cytosine. These results and data of comparative studies of nucleic acid labelling by [2-14C]thymine and [5-methyl-14C]thymine suggest that the incorporation of thymine and thymidine into nucleic acids of A. nidulans and S. aquatilis is accompanied by demethylation of these precursors. In this respect blue-green algae resemble fungi and certain green algae. 相似文献
4.
PROVENANCE OF THE ACETYL GROUP OF ACETYLCHOLINE AND COMPARTMENTATION OF ACETYL-CoA AND KREBS CYCLE INTERMEDIATES IN THE BRAIN IN VIVO 总被引:16,自引:14,他引:2
—The origin of the acetyl group in acetyl-CoA which is used for the synthesis of ACh in the brain and the relationship of the cholinergic nerve endings to the biochemically defined cerebral compartments of the Krebs cycle intermediates and amino acids were studied by comparing the transfer of radioactivity from intracisternally injected labelled precursors into the acetyl moiety of ACh, glutamate, glutamine, ‘citrate’(= citrate +cis-aconitate + isocitrate), and lipids in the brain of rats. The substrates used for injections were [1-14C]acetate, [2-14C]acetate, [4-14C]acetoacetate, [1-14C]butyrate, [1, 5-14C]citrate, [2-14C]glucose, [5-14C]glutamate, 3-hydroxy[3-14C]butyrate, [2-14C]lactate, [U-14C]leucine, [2-14C]pyruvate and [3H]acetylaspartate. The highest specific radioactivity of the acetyl group of ACh was observed 4 min after the injection of [2-14C]pyruvate. The contribution of pyruvate, lactate and glucose to the biosynthesis of ACh is considerably higher than the contribution of acetoacetate, 3-hydroxybutyrate and acetate; that of citrate and leucine is very low. No incorporation of label from [5-14C]glutamate into ACh was observed. Pyruvate appears to be the most important precursor of the acetyl group of ACh. The incorporation of label from [1, 5-14C]citrate into ACh was very low although citrate did enter the cells, was metabolized rapidly, did not interfere with the metabolism of ACh and the distribution of radioactivity from it in subcellular fractions of the brain was exactly the same as from [2-14C]pyruvate. It appears unlikely that citrate, glutamate or acetate act as transporters of intramitochondrially generated acetyl groups for the biosynthesis of ACh. Carnitine increased the incorporation of label from [1-14C]acetate into brain lipids and lowered its incorporation into ACh. Differences in the degree of labelling which various radioactive precursors produce in brain glutamine as compared to glutamate, previously described after intravenous, intra-arterial, or intraperitoneal administration, were confirmed using direct administration into the cerebrospinal fluid. Specific radioactivities of brain glutamine were higher than those of glutamate after injections of [1-14C]acetate, [2-14C]acetate, [1-14C]butyrate, [1,5-14C]citrate, [3H]acetylaspartate, [U-14C]leucine, and also after [2-14C]pyruvate and [4-14C]acetoacetate. The intracisternal route possibly favours the entry of substrates into the glutamine-synthesizing (‘small’) compartment. Increasing the amount of injected [2-14C]pyruvate lowered the glutamine/glutamate specific radioactivity ratio. The incorporation of 14C from [1-14C]acetate into brain lipids was several times higher than that from other compounds. By the extent of incorporation into brain lipids the substrates formed four groups: acetate > butyrate, acetoacetate, 3-hydroxybutyrate, citrate > pyruvate, lactate, acetylaspartate > glucose, glutamate. The ratios of specific radioactivity of ‘citrate’ over that of ACh and of glutamine over that of ACh were significantly higher after the administration of [1-14C]acetate than after [2-14C]pyruvate. The results indicate that the [1-14C]acetyl-CoA arising from [1-14C]acetate does not enter the same pool as the [1-14C]acetyl-CoA arising from [2-14C]pyruvate, and that the cholinergic nerve endings do not form a part of the acetate-utilizing and glutamine-synthesizing (‘small’) metabolic compartment in the brain. The distribution of radioactivity in subcellular fractions of the brain after the injection of [1-14C]acetate was different from that after [1, 5-14C]citrate. This suggests that [1-14C]acetate and [1, 5-14C]citrate are utilized in different subdivisions of the ‘;small’ compartment. 相似文献
5.
Guido van den Thillart Rien Verbeek 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1982,149(1):75-81
Summary Goldfish acclimated to normal oxygen levels and to 20°C were made anoxic and injected i.p. with U-14C-glucose, 6-14C-glucose, U-14C-lactate, 3-14C-lactate, 1-14C-acetate or 3,4-14C-glutamate. Radioactivity released into the water (total14C and14CO2) was monitored over a period of about 12 h. With the exception of 3,4-14C-glutamate from which only 4% was released, the release of14C from the other compounds was found to be over 30%. The fraction of the radioactivity released as CO2 varied with the compound injected but was high during the first 4 h after injection. It is argued that the acid-stable14C component is ethanol, which arises by the combined action of a modified pyruvate dehydrogenase and of alcohol dehydrogenase in muscle (Shoubridge and Hochachka 1980; Mourik et al. 1982).14CO2 release from 3-14C-lactate, 6-14C-glucose, 3,4-14C-glutamate and 1-14C-acetate cannot be explained by ethanol fermentation. Neither was there a stoichiometric relation between14CO2 and14C-ethanol release after U-14C-glucose and U-14C-lactate injection. It is concluded that at least 20% of the CO2 released is produced by Krebs cycle activity. 相似文献
6.
Isotopic studies of carbohydrate metabolism during basidiospore germination in Schizophyllum commune
Summary The metabolism and fate of specifically labeled glucose-14C were compared to mannitol-l-14C and arabitol-l-14C during basidiospore germination of Schizophyllum commune on glucose-asparagine minimal broth. Glucose-l-14C metabolism led to more 14CO2 evolution than glucose-6-14C in spores and the former activity increased upon germination. Liberation of 14CO2 from glucose-3,4-14C increased at 8 h to 12 h of germination and exceeded the amount of radioactive 14CO2 released from glucose-1-14C. The 14CO2 released from glucose-2-14C increased continually during germination while only minor changes in 14CO2 evolution occurred with glucose-6-14C. Unlabeled ethanol (0.25 M) inhibited 14CO2 evolution with glucose-3,4-14C and ungerminated spores and this inhibition disappeared upon germination.More 14CO2 was evolved from labeled glucose during germination and less radioactivity became associated with cellular material. Of the latter, alcohol-soluble extracts of spores or germlings contained mainly radioactive trehalose, less mannitol and little or no labeled arabitol, and this decreased upon germination. Germlings also converted more radioactive glucose-14C into KOH-insoluble material and KOH-soluble components. Spores or germlings converted arabitol-1-14C primarily into trehalose and this was not the case for mannitol-1-14C. 相似文献
7.
The biosynthesis of the morphinandienone alkaloids norsinoacutine, sinoacutine and flavinantine has been studied using 1-3 H-sinoacutine, 1-3H-norsinoacutine, 1-3H-norsinoacutinols, l-[S-methyl-14C]-methionine, glycine-2-14C, 1-3H-8,14-dihydronorsalutaridine, 1-3 H-8,14-dihydrosalutaridine, 1-3H-sinomenine, 1-3H-isosinomenine, (±)-[2-14C]phenylalanine, (±)-[N-methyl-14C]orientaline and (±)-[N-methyl-14C]reticuline. 相似文献
8.
Møller BL 《Plant physiology》1974,54(4):638-643
Lysine biosynthesis in seedlings of barley (Hordeum vulgare L. var. Emir) was studied by direct injection of the following precursors into the endosperm of the seedlings: acetate-1-14C; acetate-2-14C; pyruvate-1-14C; pyruvate-2-14C; pyruvate-3-14C; alanine-1-14C; aspartic acid-1-14C; aspartic acid-2-14C; aspartic acid-3-14C; aspartic acid-4-14C; α-aminoadipic acid-1-14C; and α, ε-diaminopimelic acid-1-(7)-14C. The distribution of activity in the individual carbon atoms of lysine in the different biosynthetic experiments was determined by chemical degradation. The incorporation percentages and labeling patterns obtained are in agreement with the occurrence of the diaminopimelic acid pathway. The results do not fit the incorporation percentages and labeling patterns expected if the α-aminoadipic acid pathway was operating. However, the results show that barley seedlings are able to convert a small part of the α-aminoadipic acid administered directly to lysine. 相似文献
9.
J.R. Fleeker 《Phytochemistry》1973,12(4):757-762
Ten minutes after uptake of 2,4-dichlorophenoxyacetic acid-1-14C(2,4-D-1-14C) by excised Ribes sativum leaves, 37·8 % of the radioactivity in water-soluble metabolites was in glyoxylic acid. When 2,4-D- 2-14C was supplied under the same conditions, 23·0 % of the radioactivity of the water-soluble rnetabolites was in glyoxylic acid. Radioactive glycine and glyoxylic acid, isolated from Ribes sativum 6 hr after uptake of 2,4-D-1-14C, contained essentially all of the 14C in the carboxyl-carbon atoms. When 2,4-D-2-14C was the precursor, the glycine isolated contained 64·8 % of its radioactivity in C2, while 60·0 % of the radioactivity in glyoxylic acid was in C2. The side-chain label of 2,4-D-2-14C-4-36Cl was more efficiently incorporated into ethanol-insoluble plant residue than the ring-label. The metabolism of glyoxylic acid-1-14C and 2,4-D-1-14C in excised Ribes sativum leaves were compared. The data suggest a cleavage of the acetate-moiety of 2,4-D resulting in a C2 compound, perhaps glyoxylate. 相似文献
10.
Tracer feeding experiments with Camptotheca acuminata plants show that [1′-14C]L-tryptophan, [Ar-3H4]L-tryptophan, [Ar-3H4,1′-14C]tryptophan, [1′-14C]-tryptamine, [2-14C]DL-mevalonate, and [2-14C]geraniol-[2-14C]nerol are incorporated into camptothecin. Direct stem injection of the labeled precursors into C. acuminata plants resulted in a substantial increase in the activity of isolated Camptotheca alkaloids as compared to root feeding of the same tracer. 相似文献
11.
Hartmannella culbertsoni trophozoites are transformed into viable cysts on exposure to a non-nutrient agar medium containing 15 mM MgCl2 and 20 mM taurine. Amebae differentiating in this encystment medium incorporate more uracil-2-14C into RNA and more leucine-1-14C or valine-1-14C into proteins than controls. Encysting organisms incorporate significantly more glucose-U-14C into cellulose and glucosamine-1-14C into mucopolysaccharides. Incorporation of glucose-U-14C into cellulose and of glucosamine-1-14C into mucopolysaccharides are inhibited by actinomycin D or cycloheximide. 相似文献
12.
When soybean nodules are incubated with propionate-2-14C the heme moiety of leghemoglobin becomes labeled. The incorporation of propionate-2-14C into heme is linear with time and it appears that propionate is utilized without a lag period. The rate of incorporation of propionate-2-14C into heme is more rapid than the rate of incorporation of succinate-2-14C and citrate-1,5-14C, however, these rates of incorporation may be influenced by different sizes of endogenous pools of organic acids. 相似文献
13.
《Biochimica et Biophysica Acta (BBA)/Lipids and Lipid Metabolism》1979,572(3):385-394
The metabolism of 2-amino-3-phosphono-[2-14C]propionic acid or 2-amino-3-phosphono-[3-14C]propionic acid in rats was studied in vivo and in vitro. The radioactivity in expired CO2 from the [3-14C]-labelled compound indicated the cleavage of the carbon-phosphorus (C-P) bond. A small amount of the [2-14C]-labelled compound and the [3-14C]-labelled compound was incorporated into 2-aminoethylphosphonic acid, and polar lipid of the liver and kidney contained the 2-aminoethylphosphonic acid. The 2-amino-3-phosphonopropionic acid was not detected at the lipid level. Incorporation of the [3-14C]-labelled compound into a variety of metabolites including 3-phosphonopyruvic acid and 2-phosphonoacetaldehyde suggests the transamination reaction as a decomposition mechanism of 2-amino-3-phosphonopropionic acid in mammals. 相似文献
14.
Tolbutamide partially inhibited the growth but increased the glycogen content of Tetrahymena pyriformis in logarithmically growing cultures. Tolbutamide slightly increased 14CO2 production from [1-14C] and [6-14HC] glucose and [2-14C] pyruvate, but had little effect on the oxidation of [1-14C] acetate when any of these substrates were added to the proteose-peptone medium in which the cells had been grown. Measurement of 14CO2 production from [1-14C] and [2-I4C]-glyoxylate showed that this substrate was primarily oxidized via the glyoxylate cycle, with little if any oxidation occurring via the peroxisomal glyoxylate oxidase. Addition of tolbutamide inhibited the glyoxylate cycle as indicated by a marked reduction in label appearing in CO2 and in glycogen from labeled acetate. In control cells, addition of acetate strongly inhibited the oxidation of [2-14C]-pyruvate whereas addition of pyruvate had little effect on the oxidation of [1-14C]-acetate. Acetate was more effective than pyruvate in preventing the growth inhibitory and glycogen-increasing effects of tolbutamide. The data suggest that one effect of tolbutamide may be to interfere with the transfer of isocitrate and acetyl CoA across mitochondrial membranes. 相似文献
15.
To search precursors of ethylene in banana fruits, ethylene formation from acetate-2-14C and fumarate-2,3-14C by banana slices was studied. Ethylene-14C formation from acetate-2-l4C was reduced by the addition of malonate or β-hydroxypropionate, and it was enhanced in a sealed chamber in comparison with the case in an aeration chamber. No label of fumarate-2,3-14C was incorporated into ethylene.From these facts it was suggested that acetate-2-14C was incorporated into ethylene via malonate and β-hydroxypropionate. Participation of fumarate in ethylene biosynthesis of banana fruits was ruled out. β-Hydroxypropionate was postulated as an effective precursor of ethylene formation from acetate-2-l4C. 相似文献
16.
Edward Bellion David H. Kirkley Jerry R. Faust 《Biochimica et Biophysica Acta (BBA)/General Subjects》1976,437(1):229-237
The mechanism of biosynthesis of 4-methyl-5-β-hydroxyethyl thiazole, the thiazole moiety of thiamine was studied in Salmonella typhimurium. Using the adenosine derepression technique the incorporation of various 14C-labeled precursors was determined. We found that [Me-14C]methionine, [2-14C]methionine, [U-14C]alanine, and [2-14C]glycine were not incorporated whereas [2-14C]-tyrosine was incorporated. Degradation of the 4-methyl-5-β-hydroxyethyl thiazole obtained after [2-14C]tyrosine incorporation revealed that all of the activity was located on carbon-2. These findings are discussed and compared with previous findings concerning 4-methyl-5-β-hydroxyethyl thiazole biosynthesis. 相似文献
17.
The epimastigote or culture form of Trypanosoma cruzi oxidizes [3-14C] pyruvate and [2-14C] acetate to 14CO2 without an apparent increase in overall respiration. This oxidation takes place through the tricarboxylic acid cycle as shown by (a) the incorporation of substrate 14C into cycle intermediates; (b) the earlier liberation of acetate carboxyl carbon as CO2; and (c) the characteristic intramolecular distribution of pyruvate and acetate carbon atoms in the skeletal carbon of aspartic and glutamic acids. Upon oxidation of [3-14C] pyruvate and [2-14C] acetate, two of the products, alanine and glutamic acid, are found to account for more than 50% of incorporated 14C; labeling of alanine predominates with [3-14C] pyruvate while labeling of glutamic acid predominates with [2-14C] acetate. Using [1- or 6-14C] glucose as substrate, the pattern of 14C distribution in soluble metabolites closely resembles that obtained with [3-14C] pyruvate, in accordance with the joint operation of the Embden-Meyerhof pathway and Krebs cycle. The cycle operation depends on electron transport through the mitochondrial respiratory chain, since antimycin A, at a relatively low concentration, inhibits the oxidation of [2-14C] acetate to 14CO2, to the same extent as the parasite respiration. Though functional in T. cruzi epimastigotes, the oxidative role of the Krebs’ cycle is apparently limited by the absence of an efficient oxidative apparatus. The cycle operation does, however, constitute an important source of skeletal carbon for the biosynthesis of amino acids and can contribute to the process of glycogenesis. 相似文献
18.
Leishmania donovani promastigotes in late-stationary phase incorporated label from [2-14C]acetate and [1-14C]laurate into the mannose residues of mannan, thus confirming the presence of a functional glyoxylate bypass in these parasitic protozoa. Isolated, washed calls also incorporated label from [2-14C]acetate and [1-14C]laurate into mannan during a 1-hr incubation in buffer. Glucose had no effect on label incorporation into mannan, but glutamate caused over a four-fold increase in incorporation from [2-14C]acetate and a 2.4-fold increase from [1-14C]laurate. Staurosporine, a protein kinase inhibitor that inhibits glutamate and alanine oxidation, did not inhibit label incorporation from [2-14C]acetate into mannan. Hyperosmolality caused about a 33% inhibition of label incorporation into mannan. These results show the glyoxylate cycle and/or the subsequent biosynthetic pathway from fructose-6-phosphate to mannan are subject to regulation. 相似文献
19.
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
20.
We discuss to what extent recent vibrational spectra of 14-2H, 15-2H and 14,15-2H isotopically labelled L550 provide evidence for the occurrence of 13-cis, 14-s-trans or 13-cis, 14-s-cis chromophore structures in bacteriorhodopsin's photocycle. The discussion is based on a quantum chemical (MNDO) vibrational analysis of four molecular fragments as models for the retinal chromophore in bacteriorhodopsin. 相似文献