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1.
Chloroform-soluble extracts of unpurified chloroplast preparations of lettuce, pea and spinach and of class I lettuce chloroplasts that have been incubated in the light with [methylene-3H]homogentisate contain 3H-labelled plastoquinones-9 and -8 (minor homologue), 2-demethylplastoquinones-9 and -8 (minor homologue), pytylplastoquinone and 2-demethylphytylplastoquinone.. The absence of demethylquinols, the presumed precursors of the dimethylquinones, from the extracts to the fact that no precautions were taken in the extraction procedure to present their oxidation to the corresponding quinones.In unpurified lettuce chloroplasts the synthesis of these compounds from [methylene-3H]homogentisate is Mg2+-dependent and it is stimulated by light. The addition of isopentenyl pyrophosphate to the incubation mixtures increases the amounts of both groups of quinones (polyprenyl quinones and phytyl quinones) synthesised in the light and the amounts of polyprenyl quinones synthesised in the dark. Replacement of isopentenyl pyrophosphate with a source of preformed polyrenyl pyrophosphates brings about a marked rise in the amounts of polyprenyl quinones synthesized. This rise in polyprenyl quinone synthesis is further increased if the chloroplats are subjects to osmotic shock. The presence of S-adenosylmethionine increases the amounts of dimethylquinones synthesized at the expense of the demethylquinones. The implied precursor-product relationships between 2-demethylphytylplastoquinone (quinol?) and phytylplastoquinone and between the 2-demethylplastoquinones (quinols) and plastoquinones were verified in a pulse-labelling experiment. Confirmation that these quinones, or their corresponding quinols, are synthesized.  相似文献   

2.
The preparation ofa cell-free homogenate and 10000 g particulate fraction with polyprenylpyrophosphate-p-hydroxybenzoate polyprenyltransferase activity from 0 to 7-day-old blocks of compressed baker's yeast is described. The synthesis of 4-carboxy-2-triprenylphenol from p-hydroxybenzoate and FPP by the particulate fraction has been studied in some detail. In particular it has been shown that the transferase catalysing the reaction is activated by Mg2+, has a pH optima of 7 and is inhibited by phosphate buffer. Intracellular distribution studies have established that in freshly grown cells of Saccharomyces carlsbergensis the greater part of the polyprenyl transferase activity is present in the mitochondria.  相似文献   

3.
Samples of (3R)- and (3S)-4′hydroxyphenyl[3-2H1, 3-3H]pyruvate were prepared by taking advantage of the known stereospecificity of phenylpyruvate keto-enol isomerase (tautomerase). 4′-Hydroxyphenyl[3-14C]pyruvate was obtained by the action of l-amino acid oxidase on dl-[3-14C]tyrosine, whereas a simple base-catalyzed exchange procedure yielded samples of 4′-hydroxyphenyl[3-3H]- and 4′-hydroxyphenyl[3-2H2]pyruvate. All labeled samples were converted in situ into the corresponding homogentisic acids on 4′-hydroxyphenyl-pyruvate dioxygenase that is known to catalyze the migration of the acetate side chain with retention of configuration. The isolated doubly labeled homogentisic acids were incubated with chloroplasts from Raphanus sativus cv. saxa Treib, and from the lipophilic products a fraction containing inter alia tocopherol, tocoquinone, and plastoquinone was obtained by chromatographic procedures. The incorporation of radioactivity was between 0.5 and 11% based on homogentisate. Reductive acetylation of the quinones yielded crystalline diacetylhydroquinones, which were submitted to Kuhn-Roth degradation. The radioactive acetate samples thus obtained were analyzed for chirality by an enzymatic procedure previously published. (2R)-[2-2H1, 2-3H]Homogentisate gave mainly (S)-acetate, whereas (2S)-[2-2H1, 2-3H]homogentisate was converted mainly into (R)-acetate. It is concluded that the decarboxylation of the side chain occurred with stereochemical retention during the biosynthetic process.  相似文献   

4.
Tracer experiments with 14C-labelled precursors in Iris × hollandica cv. Wedgwood, Roseda lutea L. and Reseda Odorata L. have demonstrated that 3-(3-carboxyphenyl)alanine and 3-(3-carboxy-4-hydroxyphenyl)alanine can be derived from the corresponding pyruvic acids, presumably by unspecific trans-aminations, and that (3-carboxyphenyl)glycine and (3-carboxy-4-hydroxy-phenyl)glycine can be derived from the corresponding phenylglyoxylic acids The glycine derivatives are derived from the alanine derivatives, and the corresponding mandelic acids are intermediates in these transformations. The corresponding phenylacetic acids are incorporated only slightly into the glycine derivatives, indicating that oxidation at the benzylic position in the C6–C3 compounds takes place early in the transformation. The corresponding cinnamics acids are not metabolized at all in the plants.  相似文献   

5.
Photosynthesis experiments with 14CO2 established that of 16 Droseraceae species tested Drosophylum lusitanicum incorporated the highest amount of label into plumbagin (2-methyl-5-hydroxy-1,4-naphthoquinone). Tyrosine-[β-14C] fed to Drosophyllum was shown to label plumbagin efficiently (20% incorporation). Extensive chemical degradation of the labeled naphthoquinone showed, however, that the incorporation of tyrosine was indirect, the label being distributed throughout the molecule. It was established that plumbagin and the closely related 7-methyljuglone are biosynthesized via the acetate-polymalonate pathway. Tyrosine is broken down to acetate in this tissue via the homogentisate pathway, which was demonstrated by feeding and incorporation of label into plumbagin of intermediates such as homogentisate-[14C], maleyl- and fumarylacetoacetate-[14C]. Simultaneous application of tyrosine-[β-14C] and α,α′-bipyridyl, an inhibitor of the homogentisate oxigenase, led to an accumulation of homogentisate-[14C] within the tissue. The degradation of tyrosine to acetate by Drosophyllum is not due to epiphytic bacteria since ring cleavage of tyrosine and formation of plumbagin from breakdown products occurred both within sterile grown plants and sterile cell suspension cultures. In tissue kept in darkness, plumbagin undergoes a slow turnover with a half life of about 400 hr.  相似文献   

6.
Intact, isolated spinach chloroplasts incorporated 14C from 14CO2 into plastoquinone and β-carotene under photosynthetic conditions. Addition of unlabelled l-tyrosine, p-hydroxyphenylpyruvate, or homogentisate increased the incorporation of 14C into plastoquinone, but decreased that into β-carotene.  相似文献   

7.
14C-labelled shikimic acid and double labelled shikimic acid tritiated stereospecifically at C-6 are incorporated into 3-(3-carboxyphenyl)alanine, 3-(3-carboxyl-4-hydroxyphenyl)alanine, phenylalanine, and tyrosine in Resda lutea L., Reseda odoratta L., Iris x Hollandica cv. Prof. Blauw, and Iris x hollandica cv. Wedgwood. The experiments with 14C-labelled shikimic acid confirm that the aromatic carboxyl groups and rings in 3-(3-carboxyphenyl)-alanine and 3-(3-carboxy-4-hydroxyphenyl)alanine derive from the carboxyl group and ring in shikimic acid whereas the experiments with double labelled shikimic acid demonstrate that the pro-6S-hydrogen atom is retained and the pro-6R-hydrogen atom lost in the biosynthesis of 3-(3-carboxyphenyl)alanine, phenylalanine, and tyrosine in the plants used. 3H was located in the ortho-position in the aromatic rings of phenylalanine and tyrosine but in a position para to the alanine side chain of 3-(3-cabroxyphenyl)alanine. No 3H was found in 3-(3-carboxy-4-hydroxyphenyl)alanine. This supports a derivation of the last two compounds from chorismic acidvia isochorismic acid, isoprephenic acid, and 3′-carboxyphenylpyruvic acid and 3′-carboxy-4′-hydroxyphenylpyruvic acid. The 3H/14 C ratio in 3-(3-carboxyphenyl)alanine was found higher than in the precursor used. This isotope effect must operate by competition between the pathways from isoprephenic acid to 3′-carboxyphenylpyruvic acid and to 3′-carboxy-4′-hydroxyphenylpyruvic acid. The proposed biosynthetic pathways for the two carboxy-substituted amino acids are in agreement with their distribution patterns in the plant kingdom and suggest that they may derive from minor changes of enzymes involved in the general pathways of aromatic biosynthesis.  相似文献   

8.
Feeding experiments have shown that 2′-7-dihydroxy-4′-methoxy-isoflavone-[Me-14C] and -isoflavanone-[Me-14C] are efficient precursors of the phytoalexins demethylhomopterocarpin, sativan and vesitol in CuCl2-treated lucerne (Medicago sativa) seedlings. Demethylhomopterocarpin-[Me-14C] was also incorporated into sativan and vestitol, and vestitol-[Me-14C] was incorporated into demethylhomopterocarpin and sativan. Thus, the pterocarpan demethylhomopterocarpin and the 2′-hydroxy-isoflavan vestitol are interconvertible in M. sativa, but incorporation data, and the results of kinetic feeding experiments with l-phenylalanine-[U-14C] suggest that these compounds are synthesized simultaneously from a common intermediate, which could be involved in the interconversion. A carbonium ion, derived from an isoflavanol, a likely intermediate in the biosynthetic reductive sequence from 2′,7-dihydroxy-4′-methoxy-isoflavone and -isoflavanone, is proposed as this common intermediate. 7-Hydroxy-2′,4′-dimethoxyisoflavone-[4′-Me-14C] was a very poor precursor of all three phytoalexins. Sativan, then, is most probably derived by methylation of vestitol. The incorporation of vestitol-[Me-14C] into demethylhomopterocarpin, but not into maackiain, pterocarpan phytoalexins of red clover (Trifolium pratense), is also demonstrated.  相似文献   

9.
Isothujone (trans-thujan-3-one) was formed from MVA-[14C, 3H] in Tanacetum vulgare with retention of the pro-(4R) hydrogen of precursor, but with loss of the pro-(4S) hydrogen and of one hydrogen from C-5. Cell-free extracts could not sustain the formation of isothujone from MVA but yielded geraniol and nerol (3,7-dimethylocta-trans-2,6-dien-1-ol and its cis isomer) with retention of the pro-(4R) and loss of the pro-(4S) hydrogen in each case: no hydrogen was lost from C-5 of MVA in formation of geraniol, but one such atom was lost in the formation of nerol. These results support the sequence: geraniol → nerol → isothujone: in which the first two compounds (or their biogenetic equivalents) are interconverted by a redox process involving their derived aldehydes. They are not consistent with a direct pathway to nerol from C5 intermediates or with routes involving cyclisation of linalol (3,7-dimethylocta-1,6-dien-3-ol) formed directly from the C5 compounds or from geraniol. The cell-free preparations could not interconvert geraniol and nerol, their phosphates or pyrophosphates. This may be due to the inability of a prenyltransferase-isomerase multi-enzyme system to accept exogenously-supplied intermediates under these (in vitro) conditions.  相似文献   

10.
Two diastereoisomers of 4-carboxy-4-hydroxy-2-aminoadipic acid have been isolated from leaves and inflorescences of Caylusea abyssinica. Green parts of the plant also contain appreciable amounts of the two diastereoisomers of 4-hydroxy-4-methylglutamic acid, 3-(3-carboxyphenyl)alanine, (3-carboxyphenyl)glycine, 3-(3-carboxy-4-hydroxyphenyl)alanine, (3-carboxy-4-hydroxyphenyl)glycine and in low concentration 2-aminoadipic acid, saccharopine [(2S, 2′S)-N6-(2-glutaryl)lysine] and some γ-glutamyl peptides. The acidic amino acids were separated from other amino acids on an Ecteola ion exchange column with M pyridine as eluant.  相似文献   

11.
Degradation of (+)-isothujone biosynthesized by Tanacetum vulgare or Thuja plicata from acetate-[1-14C], -[2-14C] and -[2-3H3] or from CO2-[14C] at physiological concentration revealed a pattern of asymmetric labelling whereby tracer predominantly (72–98% resided in that part of the skeleton derived from IPP. This is similar to the patterns previously obtained for uptake of MVA-[2-14C] but differed from those reported in other species with acetate-[14C] as precursor. Within the IPP-derived moiety the 3 parts derived from acetate units were not equivalently labelled. Partial degradations of geraniol and (+)-pulegone formed in Pelargonium graveolens and Mentha pulegium after uptake of 14C-labelled acetate or CO2 showed that the C-2 units of the skeletons of these monoterpenes were also labelled to widely differing extents and these patterns persisted over a range of feeding and seasonal conditions. These results suggest that metabolic pools of acetyl-CoA and/or acetoacetyl-CoA exist in these plants. The general occurrence of such pools and the consequent nonequivalent labelling patterns in secondary metabolism could invalidate biosynthetic conclusions drawn from partial degradations of labelled natural products.  相似文献   

12.
Feeding experiments have demonstrated the specific incorporation of radioactivity from dl-phenylalanine-[1-14C], l-phenylalanine-[U-14C], sodium acetate-[2-14C] and l-methionine-[methyl-14C] into the 3-benzylchroman-4-one eucomin in Eucomis bicolor. The labelling patterns indicate that eucomin is biosynthesized by the addition of a carbon atom derived from methionine onto a C15 chalcone-type skeleton. Radioactivity from 2′,4′,4-trihydroxy-6′-methoxychalcone-[methyl-14C] and 2′,4′-dihydroxy-4,6′-dimethoxychalcone-[6′-methyl-14C] was incorporated into eucomin, the latter compound being the better precursor, demonstrating the feasibility that 2′-methoxychalcones are biosynthetic precursors of the “homoisoflavonoids”. Possible biosynthetic relationships in this class of compounds are discussed.  相似文献   

13.
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   

14.
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   

15.
Radioactive gangliosides, N-[14C]-acetylneuraminylgalactosylglucosylceramide ([14C]GM3) and N- [14C]-acetylneuraminylgalactosyl-N-acetylgalactosaminyl- [N-acetylneuraminyl]-galactosylglucosylceramide ([14C]GD1a), were synthesized from CMP-[14C]sialic acid and the appropriate precursor glycolipid using specific sialyltransferase activities. These compounds were isolated and used as substrates to assay sialidase activity in HeLa cells. Although sodium butyrate added to the culture medium increased GM3 biosynthesis in HeLa cells, sialidase activity, as well as that of other glycohydrolases, was the same in control and butyrate-treated HeLa cells. The same sialidase activity appeared to hydrolyze both [14C]GM3 and [14C]GD1a, but not fetuin; the enzyme had a pH optimum of 5.0 and a Km of 75 μm for the ganglioside substrates. Although the cells contained a high sialidase activity (4–7 nmol/mg of protein/h) and could bind exogenously added [14C]GM3, no “ecto”-sialidase activity would be detected in intact cells under conditions where a close to physiological pH is maintained. The results indicate that ganglioside sialidase is not involved directly in the morphological and biochemical differentiation induced in HeLa cells by exposure to sodium butyrate.  相似文献   

16.
The CH2Cl2 and MeOH extracts from leaves of Piper caldense were subjected to chromatographic separation procedures to afford the new prenylated benzoic acid, caldensinic acid (3-[(2′E,6′E,10′E)-11′-carboxy-3′,7′,15′-trimethylhexadeca-2′,6′,10′,14′-tetraenyl]-4,5-dihydroxybenzoic acid) whose structure was determined by spectral analysis, mainly NMR (1H, 13C, HSQC, HMBC) and ESI-MS. The natural compound and derivatives displayed antifungal activity against the phytopathogenic fungi Cladosporium cladosporioides and C. sphaerospermum by direct bioautography.  相似文献   

17.
The assimilation and utilization of the individual carbon atoms of pyruvate and acetate by cells of Thiobacillus thioparus and T. neapolitanus, in the presence and absence of an energy source, were studied by use of radioactive substrates. Both organisms produced 14CO2 from 14C-labeled pyruvate, but more came from carbon 1 than from carbons 2 or 3. The conversion of the carbons of acetate to CO2 by both organisms was much less than that from any of the pyruvate carbons. When labeled pyruvate and acetate were incubated with these organisms, small amounts of radioactivity were found in the tricholoacetic acid-soluble material, nucleic acids, and lipids, and larger amounts were found in the protein fraction. The composition of the incubation medium affected the amount of utilization and incorporation of labeled substrates by both organisms. The presence of an exogenous energy source (Na2S2O3) suppressed incorporation of the labeled substrates into various cellular components by T. thioparus, but enhanced incorporation by T. neapolitanus. When 14C-pyruvate was used as a substrate, as many as 12 radioactive compounds were found in the water-soluble fraction in the experiments with T. neapolitanus, whereas no more than three radioactive compounds were detected in this fraction in the experiments with T. thioparus. Of the total 14C activity found in the water-soluble fractions, malic acid contained the highest percentage. These findings are discussed in light of the overall metabolism of these two sulfur-oxidizing obligate chemoautotrophs, as well as in relation to the biochemical basis of chemoautotrophy.  相似文献   

18.
1. Slices of liver from laying hens incorporated Na214CO3 and NaH232PO4 into phosvitin. Slices of liver from immature birds did not do so to any appreciable extent. The 32P was incorporated into O-phosphorylserine in the phosvitin molecule. 2. Kidney, spleen, muscle, large and small intestine, ovary and oviduct from laying birds did not incorporate Na214CO3 into phosvitin. 3. Slices of liver from laying hens carried out a net synthesis of phosphoprotein under the standard conditions of incubation. Slices from the livers of immature pullets did not do so. 4. Liver from the laying hen incorporated [2-14C]glycine, [3-14C]serine and [2-14C]glutamic acid into phosvitin. Part of the glycine was shown to be present as serine in the final product. 5. Slices of liver from immature birds treated with oestradiol synthesized phosvitin from [2-14C]glycine, but the addition of oestrogens in vitro to slices from untreated immature birds did not promote synthesis during a 3 hr. incubation period.  相似文献   

19.
Isolation and identification of l-3-carboxy-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline and l-1-methyl-3-carboxy-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline from seeds and callus of S. hassjoo are described. Administration of [β-14C]-labelled DOPA to a callus culture of this legume resulted in the incorporation of radioactivity into l-3-carboxy-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline, l-1-methyl-3-carboxy-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline and stizolobic acid, which was confirmed by constant specific radioactivity after co-crystallization with authentic samples of each compound.  相似文献   

20.
A series of 5-imino-4-thioxo-2-imidazolidinone derivatives with different substituents at N1 and N3 was synthesized with high yield and excellent purity by the reaction of different N-arylcyanothioformamide derivatives with isocyanate derivatives. Treatment 5-imino-4-thioxo-2-imidazolidinone derivatives with acidic medium afforded 4-thioxoimidazolidin-2,5-dione derivatives. The structures of the obtained products were established based on spectroscopic IR, 1H NMR, 13C NMR, 1H, 1H-COSY, HSQC and elemental analyses. The anti-inflammatory activity of the synthesized compounds through the carrageenan-paw edema model as well as in vitro COX-1 and COX-2 inhibition assay were evaluated where most of the synthesized compounds showed significant anti-inflammatory activity. Mostly, all of our synthesized compounds have greater activity more than celecoxib toward both cyclooxygenase enzymes. All of the tested compounds (except one compound) exhibited IC50 valves for COX-2 ranged from 0.001 × 10−3 to 0.827 × 10−3 µM while the reference drug has IC50 40.0 × 10−3 µM. Furthermore, the analgesic activity of such compounds was also determined. Molecular modeling study was also conducted to rationalize the potential as anti-inflammatory agents of our synthesized compounds by predicting their binding modes, binding affinities and optimal orientation at the active site of the COX enzymes.  相似文献   

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