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1.
The incorporation of (±)-coclaurine, (±)-norcoclaurine, (±)-N-methylcoclaurine and didehydro-N-methyleoclaurinium iodide into tetrandrine in Cocculus laurifolius has been studied and specific utilization of (±)-N-ethylcoclaurine demonstrated. The evidence indicates that tetrandrine is formed in the plants by oxidative dimerization of N-methylcoclaurine. Double labelling experiment with (±)-N- [14C]-methyl- [1-3H]-coclaurine demonstrated that the hydrogen atom at the asymmetric centre in the 1-benzylisoquinoline precursor is retained in the bioconversion into tetrandrine. Parallel feedings of (+)-(S)- and (?)-(R)-N-methylcoclaurines showed that the stereospecificity is maintained in the biosynthesis of tetrandrine from the 1-benzylisoquinoline precursor. 相似文献
2.
dl-?-N-Methyl-3H-lysine-2-14C was prepared and administered to excised shoots of Sedum acre from which dl-sedamine was isolated. The ?-N-methyllysine was not incorporated without degradation and, therefore, it is probably not a direct precursor of the piperidine ring of sedamine. 相似文献
3.
Anil.K. Tyagi David A. Cooney Marianna Bledsoe Hiremagalur N. Jayaram 《Journal of biochemical and biophysical methods》1980,2(3):123-132
Two complementary methods have been devised for measuring the activity of 5-amino-4-imidazole-N-succinocarboxamide ribonucleotide synthetase (SAICAR synthetase, EC 6.3.2.6), a critical enzyme in the pathway of purine biosynthesis. In the first method, l-[4.14C]aspartic acid is condensed with 5-amino-4-imidazolecarboxylic acid ribonucleotide (AICOR) via the action of SAICAR synthetase. Unreacted l-[4-14C]aspartic acid is measured by scintillation spectrometry. In the second method, the reverse reaction of SAICAR synthetase is measured; radiactive 5-amino-4-imidazole-N-succinocarboxamide ribonucleotide (SAICAR) is synthetized enzymatically, using a partial purified preparation of SAICAR synthetase from chicken liver. To the purified [14C]SAICAR is added: sodium arsenate, Tris-HCl buffer containing ADPMgCl2 or buffer alone, and to initiate the reaction, a 12 000 × g supernatant or other suitable source of enzyme. As a consequence of the arsenolytic cleavage of [14C]SAICAR, l-[4-14C]aspartic acid is generated in stoichiometric amounts. The fourth carbon of this amino acid is then detached by selective enzymatic decarboxylation, trapped in 40% KOH and quantitated by scintillation spectrometry. The assays, performed as prescribed, are facile and notably sensitive; using them, the specific activity of SAICAR synthetase has been measured in acetone powders of the livers of representative members of the Vertebrata, and also in the principal viscera of the mouse. Of the livers examined, pigeon liver was the richest source of the investigated enzyme. 相似文献
4.
By using two different isotopically labelled precursors and ion exchange aminoacid analysis, it is shown that the methyl group of methionine is incorporated into ε-N-mono-, di- and trimethylated derivatives of lysine found in the free state in the cells of Neurospora crassa. The possibility that lysine methylation can take place not only via protein bound-lysine but also directly on the free aminoacid, or a derivative is considered. 相似文献
5.
The metabolisms of glucose, fructose, shikimate, phenylalanine, tyrosine and myoinositol in Humulus lupulus (hop) were studied. The results of these investigations lend support to the hypothesis, that the formation of the six membered ring of the hop bitter compounds proceeds via polyketides but not via shikimate. 相似文献
6.
Experiments with ent-kaur-16-ene-[14C], prepared biosynthetically from sodium acetate-[2-14C], have shown that the C-20 carbon atom of the C20 gibberellins is evolved as carbon dioxide during the biosynthesis of the C19 gibberellins by Gibberella fujikuroi. 相似文献
7.
Anand Akhila 《Phytochemistry》1985,24(11):2585-2587
Use of [14C,3H]-labelled precursors revealed that leaf blades of Cymbopogon flexuosus converted geraniol (3,7-dimethylocta-trans-2,6-diene-1-ol) into citral-trans with loss of pro-(1S) hydrogen whereas nerol lost the pro-(1R) hydrogen while being converted into citral-cis. Secondly, the citral-trans is converted into citral-cis and vice versa and there is no separate route for the biosynthesis of either of the two aldehyde isomers. 相似文献
8.
Homocysteine-dependent transmethylases utilizing 5-methyltetrahydropteroylglutamic acid and S-adenosylmethionine as methyl donors have been examined using ammonium sulphate fractions prepared from isolated mitochondria of pea cotyledons. Substantial levels of a 5-rnethyltetrahydropteroylglutamate transmethylase were detected, the catalytic properties of this enzyme being found similar to those of a previously reported enzyme present in cotyledon extracts. The mitochondrial 5-CH3-H4PteGlu transmethylase had an apparent Km of 25 μM for the methyl donor, was saturated with homocysteine at 1 mM and was inhibited 50% by l-methionine at 2.5 mM. At similar concentrations of methyl donor the mitochondrial S-adenosylmethionine methyltransferase was not saturated. Mitochondrial preparations were found capable of synthesizing substantial amounts of S-adenosylmethionine but lacked ability to form S-methylmethionine. Significant levels of β-cystathionase, cystathionine-γ-synthase, l-homoserine transacetylase and l-homoserine transsuccinylase were detected in the isolated mitochondria. The activity of the enzymes of homocysteine biosynthesis was not affected by l-methionine in vitro. It is concluded that pea mitochondria have ability to catalyze the synthesis of methionine de novo. 相似文献
9.
Houseflies ovariectomized within 12 h after emergence do not produce (Z)-9-tricosene nor demonstrate the shift from alkene to alkane synthesis that is typcal of flies with developing ovaries. A single injection of 20-hydroxyecdysone at doses of 0.1 to 10 μg will induce the pattern in ovariectomized insects that is characteristic of flies with ovaries. Furthermore, this pattern persists for 3 days, but by 6 days after hormone injection, the synthesis of (Z)-9-tricosene stops and more alkenes are produced than alkanes. A post-hormone treatment time of 16 h was required before detectable amounts of (Z)-9-tricosene appeared on ovariectomized flies. Multiple injections of 20-hydroxyecdysone at doses of 50 ng into ovariectomized flies induced (Z)-9-tricosene synthesis and a shift in alkene to alkane synthesis. Thus, 20-hydroxyecdysone was able to act as an ovarian substitute in ovariectomized flies by stimulating pheromone synthesis. 相似文献
10.
In Euglena gracilis Z the biosynthesis of spermidine and spermine closely resembles the pathways occurring in mammalian tissues and in most microorganisms. l-Ornithine and not l-arginine, as is the case in most plants, is the main precursor of putrescine, and S-adenosylmethionine donates the propylamino moiety for the biosynthesis of spermidine and spermine. Cell-free extracts of Euglena synthesized sym-norspermidine and sym-norspermine from 1,3-diaminopropane and labelled S-adenosylmenthionine. The synthases for the biosynthesis of these two polyamines have a pH optimum of 7.6, like that of spermidine and spermine synthases. Ion exchange chromatography showed two peaks corresponding to the retention times of 2,4-diaminobutyric acid and 1,3-diaminopropane, lower homologues of ornithine and putrescine, respectively. Experiments with dl-2,4-diaminobutyric acid-[4-14C] did not result in significant incorporation of the label into 1,3-diaminopropane. 相似文献
11.
William J. Keller 《Phytochemistry》1980,21(12):2851-2852
Living Dolichothele sphaerica metabolized 1.91% of administered [2-14Clphenylalanine to N- methylphenethylamine. Phenethylamine, the presumable intermediate in this biosynthetic conversion, was detected in an extract of the cactus in very low concentrations. The addition of carrier to the extract allowed the isolation of radiolabelled phenethylamine and the establishment of its probable involvement in N- methylphenethylamine formation. This is the first report of N- methylphenethylamine biosynthesis, of phenyl- alanine serving as an efficient precursor to cactus alkaloids, and of the occurrence of phenethylamine in the Cactaceae. 相似文献
12.
Sabah Hassan Ahmed Atef Hani M. Ali Rahma Alshamrani Ahmed Ramadan 《Saudi Journal of Biological Sciences》2022,29(5):3647-3653
The major reports on Calotropis procera (C. procera) indicated the importance of this plant as a resource of pharmaceutically active ingredients as well as its medical advantages. β-amyrin (BA) is a significant substance in this plant and has a pharmacological effects in some frameworks, like focal and fringe sensory system, digestive and immune systems. In this study, the impact of sunlight before and after irrigation on the BA production in C. procera is studied its pathway with involved eight key enzymes. The eight enzymes' genes were characterized and successfully submitted to NCBI; AAS (acc.no. KU997645) for α-amyrin synthase, BAS (acc.no. MW976955) for β-amyrin synthase, SE (acc.no. MW976956) for squalene epoxidase, SS (acc.no. MW976957) for squalene synthase, GPPS, (acc.no. MW976958) for geranyl pyrophosphate synthase, FPPS (acc.no. MW976959) for farnasyl pyrophosphate synthase, CAS1, (acc.no. MZ00598) for cycloartenol synthase1 and LS (acc.no. MZ005982) for lupeol synthase. qRT-PCR analysis revealed high expression levels of GPPS, FPPS, SS, SE, and BAS genes at all times specially midday. Otherwise, CAS1, LS and BAS expression levels were very low at all daylight periods. The UPLC β-amyrin data are in accordance with qRT-PCR results. This indicates that triterpenes biosynthetic pathway in C. procera is going to β-amyrin accumulation with the highest level at midday. 相似文献
13.
Ring-labelled 7-methylxanthosine was synthesized and fed to leaves of Coffea arabica. Up to 26% of the tracer was converted into caffeine within 8 days. 相似文献
14.
The production of labelled aliphatic hydrocarbons in Anacystis montana and Botryococcus braunii has been studied using Na2CO3 [14C] as a carbon source. The major hydrocarbon produced by A. montana is pentadecane (ca 93%) accompanied by a pentadecene (ca 4%) and other hydrocarbons in the range C13-C17. Long chain (C21-C 33) hydrocarbons could not be detected in this organism. The variety of unsaturated hydrocarbons (C25-C31) previously reported in Botryococcus braunii is confirmed and contrasts with the synthesis of unsaturated C17 hydrocarbons only, in axenic cultures prepared from single cell isolates of this colonial alga. 相似文献
15.
A 13C-NMR study of the biosynthesis of daunomycin adriamycin from propionate[1-13C] has been carried out in cultures of Streptomyces peucetius var. caesius. Results give direct support for the postulate that a propionate ‘starter’ is involved in the biosynthesis of both metabolites. 相似文献
16.
The amounts of d-alanine derivatives, γ-l-glutamyl-d-alanine and N-malonyl-d-alanine, increase rapidly during the early growth of pea seeds. Pyruvate-[1?14C], l-alanine-[U?14C], d-alanine-[U?14C], l-alanine-[15N] and 15NH4Cl were therefore fed to the seedlings and the incorporation investigated. Labelling results revealed that pea seedlings can utilize these erogenous compounds to form d-alanine and that labelled l-alanine is effectively converted to the d-enantiomer with retention of 14C and, largely, 15N label. Enzyme analyses in vitro provided additional evidence that the extract of pea seedlings catalyzes the direct conversion of l-alanine to d-alanine. The data suggest that the de novo synthesis of d-alanine in pea seedlings occurs by a racemase reaction. 相似文献
17.
Degradation of geraniol (3,7-dimethylocta-trans-2,6-dien-1-ol) biosynthesized in Rosa dilecta has proved that C-10 is exclusively derived from C-2 of mevalonate. This verifies the generally accepted but hitherto unproven view of the origin of the gem-methyls in this compound and of the corresponding groups in other terpenoids. 相似文献
18.
In contrast to earlier results [1-14C] acetate, [2-14C] malonate and [n 9,10-3H] oleate show significant incorporations into wyerone and related Vicia faba phytoalexins, following infection by Botrytis cinerea. 相似文献
19.
20.
William J. Keller 《Phytochemistry》1980,19(3):413-414
-Administration of tyramine-[1-14C] to Opuntia clavata resulted in the formation of labeled N-methyltyramine. This procedure established the biosynthetic origin of the major alkaloid in this cactus as well as providing a radiolabeled chemical that was not commercially available. The N-methyltyramine-[1-14C] was in turn administered to Coryphantha macromeris var. runyonii to determine its metabolic role in the biosynthesis of the psychoactive cactus alkaloid normacromerine (N-methyl-3,4-dimethoxy-β-hydroxyphenethylamine). This feeding experiment established N-methyltyramine as a precursor to normacromerine. 相似文献