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1.
Two genes, orf6 and orf9 located in the L-oleandrose sugar biosynthetic gene cluster of Streptomyces antibioticus Tü99. NovU has been characterized as C-5 methyltrnaferase involved in noviose biosynthetic pathway. We have cloned and heterologously expressed the orf6, orf9, and novU genes in S. venezuelae YJ003-OTBP1. This established the function of orf6 and orf9 as 4-ketoreductase and 3-epimerase, respectively. All of analytical data of the noviosylated 10-deoxymethynolide also is in support of proving their functions. Furthermore biosynthetic pathway 5,5-gem-dimethyl-6-deoxyglucose (TDP-Lnoviose) has been proposed.  相似文献   

2.
We previously isolated and characterized a new free amino acid withd-configuration at the α-carbon,trans-3, 4-dehydro-d-2-aminopimelic acid and its related amino acids,d-2-aminopimelic acid and 4-hydroxy-l-2-aminopimelic acid fromAsplenium unilaterale. In this paper, we report that the biosynthetic relationshps among these three amino acids were studied using14C-and3H-labeled compounds as tracers. Glutamate and aspartate were shown to be good precursors and it was suggested that 4-hydroxy-l-2-aminopimelic acid is biosynthesized first and the twod-amino acids are derived from it. Furthermore, the distribution patterns of these non-protein amino acids inAsplenium sect.Hymenasplenium were examined in detail and they were evaluated by their biosynthetic pathway. Morphological characters especially on their rhizomes were also examined and their character phylogeny was determined by outgroup comparison. Taking all the characters available into account, the phylogenetic relationship among 7 species ofAsplenium sect.Hymenasplenium in Japan and Taiwan is discussed by the transformed cladistic method.  相似文献   

3.
The glucose 1-phosphate uridylyltransferase (GalU) is absolutely required for the biosynthesis of capsular polysaccharide, the sine qua non virulence factor of Streptococcus pneumoniae. The pneumococcal GalU protein was overexpressed in Escherichia coli, and purified. GalU showed a pI of 4.23, and catalyzed the reversible formation of UDP-glucose and pyrophosphate from UTP and glucose 1-phosphate with Km values of 0.4 mM for UDP-glucose, 0.26 mM for pyrophosphate, 0.19 mM for glucose 1-phosphate, and 0.24 mM for UTP. GalU has an optimum pH of 8–8.5, and requires Mg2+ for activity. Neither ADP-glucose nor TDP-glucose is utilized as substrates in vitro. The purification of GalU represents a fundamental step to provide insights on drug design to control the biosynthesis of the main pneumococcal virulence factor.  相似文献   

4.
Most Pseudomonas aeruginosa PAO mutants which were unable to utilize l-arginine as the sole carbon and nitrogen source (aru mutants) under aerobic conditions were also affected in l-ornithine utilization. These aru mutants were impaired in one or several enzymes involved in the conversion of N2-succinylornithine to glutamate and succinate, indicating that the latter steps of the arginine succinyltransferase pathway can be used for ornithine catabolism. Addition of aminooxyacetate, an inhibitor of the N2-succinylornithine 5-aminotransferase, to resting cells of P. aeruginosa in ornithine medium led to the accumulation of N2-succinylornithine. In crude extracts of P. aeruginosa an ornithine succinyltransferase (l-ornithine:succinyl-CoA N2-succinyltransferase) activity could be detected. An aru mutant having reduced arginine succinyltransferase activity also had correspondingly low levels of ornithine succinyltransferase. Thus, in P. aeruginosa, these two activities might be due to the same enzyme, which initiates aerobic arginine and ornithine catabolism.Abbreviations OAT ornithine 5-aminotransferase - SOAT N2-succinylornithine 5-aminotransferase - Oru ornithine utilization - Aru arginine utilization  相似文献   

5.
The function of the Waxy locus in starch synthesis in maize endosperm   总被引:1,自引:0,他引:1  
The soluble adenosine diphosphate glucose-starch glucosyltransferase of maize (Zea mays L.) endosperm uses adenosine diphosphate glucose as a sole substrate, but the starch granule-bound nucleoside diphosphate glucose-starch glucosyltransferase utilizes both adenosine diphosphate glucose and uridine diphosphate glucose. The soluble glucosyltransferase can be bound to added amylose or to maize starch granules that contain amylose. However, binding of the soluble enzyme to the starch granules does not change its substrate specificity to that of the natural starch granule-bound glucosyltransferase. Furthermore, the soluble glucosyltransferase bound to starch granules can be removed by repeated washing without a change in specificity. The bound glucosyltransferase can be released by mechanical disruption of starch granules, and the released enzyme behaves in a manner similar to that of the bound enzyme in several respects. These observations suggest that the soluble and bound glucosyltransferases are different enzymes. The starch granule-bound glucosyltransferase activity is linearly proportional to the number of Wx alleles present in the endosperm. This is compatible with the hypothesis that the Wx allele is a structural gene coding for the bound glucosyltransferase, which is important for the normal synthesis of amylose.Journal Paper No. 4818 of the Purdue University Agricultural Experiment Station.  相似文献   

6.
To develop a system for combinatorial biosynthesis of glycosylated macrolides, Streptomyces venezuelae was genetically manipulated to be deficient in the production of its macrolide antibiotics by deletion of the entire biosynthetic gene cluster encoding the pikromycin polyketide synthases and desosamine biosynthetic enzymes. Two engineered deoxysugar biosynthetic pathways for the biosynthesis of thymidine diphosphate (TDP)-d-quinovose or TDP-d-olivose in conjunction with the glycosyltransferase–auxiliary protein pair DesVII/DesVIII derived from S. venezuelae were expressed in the mutant strain. Feeding the representative 12-, 14-, and 16-membered ring macrolactones including 10-deoxymethynolide, narbonolide, and tylactone, respectively, to each mutant strain capable of producing TDP-d-quinovose or TDP-d-olivose resulted in the successful production of the corresponding quinovose- and olivose-glycosylated macrolides. In mutant strains where the DesVII/DesVIII glycosyltransferase–auxiliary protein pair was replaced by TylMII/TylMIII derived from Streptomyces fradiae, quinovosyl and olivosyl tylactone were produced; however, neither glycosylated 10-deoxymethynolide nor narbonolide were generated, suggesting that the glycosyltransferase TylMII has more stringent substrate specificity toward its aglycones than DesVII. These results demonstrate successful generation of structurally diverse hybrid macrolides using a S. venezuelae in vivo system and provide further insight into the substrate flexibility of glycosyltransferases. Won Seok Jung and Ah Reum Han contributed equally to this work.  相似文献   

7.
Glutamine synthetase (EC 6.3.1.2) was purified to homogeneity from a free-living nitrogen fixing bacteria, Bacillus polymyxa. The holoenzyme, relative molecular mass (Mr) of 600 000 is composed of monomeric sub-units of 60 000 (Mr). The isoelectric point of the sub-units was 5.2. The pH optimum for the biosynthetic and transferase enzyme activity was 8.2 and 7.8, respectively. The apparent K m values (K m app ) in the biosynthetic reaction for glutamate, NH4Cl and ATP were 3.2, 0.22 and 1 mM, respectively. In the transferase reaction the K m values for glutamine, hydroxylamine and ADP were 6.5, 3.5 and 8×10-4 mM respectively. L-Methionine-D-L-sulfoximine was a very potent inhibitor in both biosynthetic and transferase reactions. Similar to most Gram positive bacteria there was no evidence of in vivo adenylylation and the enzyme seemed to be mainly regulated by feed-back mechanism.Abbreviations PMSF phenylmethylsulfonylfluoride - TCA trichloroacetic acid - GS glutamine synthetase - MSO L-Methionine-D-L-sulfoximine - SDS-PAGE sodium dodecyl sulfatepolyacrylamide gel electrophoresis - SVPDE snake venum phosphodiesterase  相似文献   

8.
The biosynthetic origin of themethyl group in the methyl chloride produced by cultures ofPhellinus pomaceus (Pers.) Maire has been investigated using stable isotope labeled substrates. Feeding ofd-[6,6-2H2] glucose,Dl-[3,3-2H2] serine andl-[methyl-2H3] methionine led to the production of deuterated methyl chloride in which the major labeled species contained 2, 2, and 3 deuterium atoms, respectively. The data are consistent with the methyl chloride produced by this organism being derived solely from methionine with retention of all of the methyl protons.Abbreviation SAM S-adenosylmethionine - FH4 tetrahydrofolate - N5-CH3FH4 N5-methyltetrahydrofolate - B12 cobalamin  相似文献   

9.
The mevalonate-independent methylerythritol phosphate pathway is widespread in bacteria. It is also present in the chloroplasts of all phototrophic organisms. Whereas the first steps, are rather well known, GcpE and LytB, the enzymes catalyzing the last two steps have been much less investigated. 2-C-Methyl-D-erythritol 2,4-cyclodiphosphate is transformed by GcpE into 4-hydroxy-3-methylbut-2-enyl diphosphate, which is converted by LytB into isopentenyl diphosphate or dimethylallyl diphosphate. Only the bacterial GcpE and LytB enzymes have been investigated to some extent, but nothing is known about the corresponding plant enzymes. In this contribution, the prosthetic group of GcpE from the plant Arabidopsis thaliana and the bacterium Escherichia coli has been fully characterized by Mössbauer spectroscopy after reconstitution with 57FeCl3, Na2S and dithiothreitol. It corresponds to a [4Fe-4S] cluster, suggesting that both plant and bacterial enzymes catalyze the reduction of 2-C-methyl-D-erythritol 2,4-cyclodiphosphate into (E)-4-hydroxy-3-methylbut-2-enyl diphosphate via two consecutive one-electron transfers. In contrast to the bacterial enzyme, which utilizes NADPH/flavodoxin/flavodoxin reductase as a reducing shuttle system, the plant enzyme could not use this reduction system. Enzymatic activity was only detected in the presence of the 5-deazaflavin semiquinone radical.  相似文献   

10.
The objective of the present work was to determine what impact extremely high nitrogen dosages would have on proline metabolism in order to use this amino acid as a bioindicator of N status of green bean plants (Phaseolus vulgaris L. cv. Strike). In this effort, we identified the most favourable pathway of proline synthesis under our experimental conditions. The N was applied to the nutrient solution in the form of NH4NO3 at 5.4 mmol/L (N1, optimal level), 11.6 mmol/L (N2), 17.4 mmol/L (N3), and 23.2 mmol/L (N4). Our results indicate that the application of high N dosages inPhaseolus is characterized by the accumulation of NO3, NH4+ and proline in root and foliar organs. However, although the enzymes in charge of proline biosynthesis, ornithine-δ-aminotransferase (OAT, EC 2.6.1.13) and Δ1-pyrroline-5-carboxylate synthetase (P5CS, EC 2.7.2.11/1.2.2.41) vary in behaviour depending on the N status, in our experiment, this amino acid appears to be synthesized mainly by the enzyme ornithine-δ-aminotransferase. This suggests predominance of the ornithine pathway over the glutamine pathway. Finally, under our experimental conditions, proline can be defined as a good indicator of N excess of green bean plants.  相似文献   

11.
Lipopolysaccharides (LPS), isolated from four Mycoplana species, i.e. the type strains of M. bullata, M. segnis, M. ramosa and M. dimorpha, were characterized onto their chemical composition and their respective lipid A-types. Those of M. bullata and M. segnis showed on DOC-PAGE an R-type character and had lipid A's of the Lipid ADAG-type which exclusively contained 2,3-diamino-2,3-dideoxy-d-glucose as lipid A sugar. LPS's of M. ramosa and M. dimorpha showed, although only weakly expressed, ladder-like patterns on DOC-PAGE indicating some S-type LPS's and lipid A of the d-glucosamine type (Lipid AGlcN). M. bullata LPS contained mannose and glucose in major amounts and additionally l-glycero-d-mannoheptose, whereas M. segnis LPS was composed of rhamnose, mannose and glucose together with both, d-glycero-d-manno- and l-glycero-d-manno-heptoses in a molar ratio of 1:2. All LPS's contained 2-keto-3-deoxy-octonic acid (Kdo), phosphate and an unidentified acidic component X. In addition to X, M. segnis LPS contained glucuronic and galacturonic acids, whereas M. ramosa LPS contained only galacturonic acid. Acetic acid hydrolysis of the LPS resulted in splitting off lipid A moieties, very rich in 3-hydroxy fatty acids, in particular in 3-OH-12:0 (in Lipid ADAG), or in 3-OH-14:0 (in Lipid AGlcN). Analysis of the 3-acyloxyacyl residues revealed major amounts of amide-linked 3-OH(3-OH-13:0)12:0 in lipid A of M. bullata and 3-OH(12:0)12:0 in lipid A of M. segnis. The rare 4-oxo-myristic acid (4-oxo-14:0) was observed only in M. bullata LPS, where it is ester-linked. Amide linked diesters could not be traced in M. ramosa and M. dimorpha. All four lipid A's lacked erster-bound acyloxyacyl residues.Non-standard abbreviations DAG 2,3-diamino-2,3-dideoxy-d-glucose - Kdo 2-keto-3-deoxy-octonate - LPS lipopolysaccharide - PITC phenyl isothiocyanate - NANA N-acetyl neuraminic acid  相似文献   

12.
The level of lysine-6-aminotransferase (encoded by the lat gene), an enzyme that commits lysine to the cephamycin biosynthesis pathway, is very low in wild type Nocardia lactamdurans. Two lat overexpression systems (pAMEXlat and pSAFlat) were constructed to express the promoterless lat gene of N. lactamdurans from the strong promoters amyP (of the α-amylase gene) and safP (of the secretion activating factor gene) of Streptomyces griseus. Both constructions led to very high levels of lysine-6-aminotransferase (between 8- and 15-fold) in the cells. Expression of lat from the amy promoter was optimal in glycerol-containing medium and was negatively regulated by glucose. The high levels of lysine-6-aminotransferase resulted in a 50–200% increase in cephamycin C production in the standard fermentation conditions. Onset of cephamycin C biosynthesis occurred at the same time in control and in lat-overexpressing strains, but the cephamycin production rate was clearly higher in transformants overexpressing the lat gene. Furthermore, HPLC analysis of cephamycin C in the culture broths revealed an early depletion of biosynthetic intermediates and an accumulation of cephamycin C when the lat gene was overexpressed. These results indicate that lysine-6-aminotransferase activity is limiting for cephamycin C biosynthesis under some culture conditions. Received: 4 August 1999 / Received revision: 29 September 1999 / Accepted: 2 October 1999  相似文献   

13.
To elucidate the biotransformation from 5-oxomilbemycins A3 and A4 to milbemycins A3 and A4 in Streptomyces bingchengensis, the C5-ketoreductase gene (milF) was cloned using PCR with the specific primer designed from homologous nucleotide sequences. The C5-ketoreductase (MilF) was heterologously expressed in E. coli BL21 (DE3) as a His-tagged fusion protein. The characterization and biotransformation function of purified MilF was verified by in vitro enzyme assay. MilF is an NADPH-dependent reductase. The biotransformation products, analyzed by LC-APCI/MS, were identified as milbemycin A3 and milbemycin A4. MilF is thus present in Streptomyces bingchengensis and can transform 5-oxomilbemycins A3 and A4 to milbemycins A3 and A4. These findings are significant for understanding the biosynthetic pathway of milbemycins in Streptomyces bingchengensis and pave the way to obtain a producer strain of 5-oxomilbemycins directly by targeted milF disruption.  相似文献   

14.
Metabolic pathways and biotechnological production of l-cysteine   总被引:1,自引:0,他引:1  
l-Cysteine is an important amino acid both biologically and commercially. Although most amino acids are commercially produced by fermentation, cysteine is mainly produced by protein hydrolysis. However, synthetic or biotechnological products have been preferred in the market. Biotechnological processes for cysteine production, both enzymatic and fermentative processes, are discussed. Enzymatic process, the asymmetric hydrolysis of dl-2-amino-Δ2-thiazoline-4-carboxylic acid to l-cysteine, has been developed and industrialized. The l-cysteine biosynthetic pathways of Escherichia coli and Corynebacterium glutamicum, which are used in many amino acid production processes, are also described. These two bacteria have basically same l-cysteine biosynthetic pathways. l-Cysteine-degrading enzymes and l-cysteine-exporting proteins both in E. coli and C. glutamicum are also described. In conclusion, for the effective fermentative production of l-cysteine directly from glucose, the combination of enhancing biosynthetic activity, weakening the degradation pathway, and exploiting the export system seems to be effective.  相似文献   

15.
Cell suspension cultures of Eschscholtzia californica produce one or more cyanogenic compounds when placed under osmotic stress. The nature of the compound(s) has not yet been established but they are not identical with the cyanogenic glucosides triglochinin and dhurrin, which occur in the intact plant. Microsomal fractions isolated from stressed cell cultures catalyze the synthesis of 1-(4-hydroxyphenyl)-2-nitroethane from L-tyrosine. Both NADPH and molecular oxygen are required as cosubstrates, and 4-hydroxyphenylacetaldoxime is an intermediate in the synthesis of the nitrocompound. This observation indicates that the biosynthetic pathways leading from L-tyrosine to 1-(4-hydroxyphenyl)-2-nitroethane and to the L-tyrosine-derived cyanogenic glucosides are closely related. A glucosyltransferase which glucosylates the nitrocompound in the presence of uridine diphosphate glucose appears in the osmotically stressed cultures in a time pattern similar to that for production of the nitrocompound.Abbreviations HPAA 4-hydroxyphenylacetaldoxime - HPLC high-pressure liquid chromatography - HPNE 1-(4-hydroxyphenyl)-2-nitroethane - TLC thin-layer chromatography  相似文献   

16.
Summary In Serratia marcescens Sr41, l-canavanine was demonstrated to be a weak cell growth inhibitor in minimal medium containing glucose as the sole carbon source. The inhibition of cell growth was enhanced by changing the carbon source from glucose to l-glutamic acid. An arginine regulatory mutant (i.e., argR mutant) in which formation of l-arginine biosynthetic enzymes was genetically derepressed was isolated by selecting for l-canavanine resistance on the glutamate medium. Furthermore, an l-arginine-producing strain was constructed by introducing the mutation leading to feedback-resistant N-acetylglutamate synthase into the argR mutant. The resulting transductant produced about 40 g/l of l-arginine, whereas the wild strain produced no l-arginine and the argR mutant only 3 g/l.  相似文献   

17.
Interspecific hybridizations were made between species of theE. semicostatus group, viz.,E. semicostatus (Nees exSteud.)Meld.,E. validus (Meld.)B. Salomon,E. abolinii (Drob.)Tzvel., andE. fedtschenkoi Tzvel., and species of theE. tibeticus group, viz.,E. pendulinus (Nevski)Tzvel.,E. tibeticus (Meld.)Singh,E. shandongensis B. Salomon, andE. gmelinii (Ledeb.)Tzvel., as well as among species within theE. tibeticus group. All species are tetraploid (2n = 4x = 28) and possess SY genomes. Meiotic pairing data from 24 hybrids involving 17 interspecific combinations are presented. The average number of chiasmata per cell ranged from 17.91 to 26.20 in hybrids within theE. tibeticus group, compared with 7.26 to 22.04 in hybrids between the two species groups. Despite the extensive collection of cytological data, there was no definite evidence for confirming or disproving the separate existence of the two groups.  相似文献   

18.
The deoxysugar biosynthetic gene cluster of calicheamicin contains the calS7, which encodes glucose-1-phosphate nucleotidyltransferase and converts glucose-1-phosphate and nucleotides (NTP) to NDP-glucose and pyrophosphate. calS7 was expressed in Escherichia coli BL21(DE3), and the purified protein had significant thymidylyltransferase and uridylyltransferase activities as well, with some guanidylyltransferase activity but negligible cytidyl and adenyltransferase activity. The functions of thymidylyltransferase and uridylyltransferase were also verified using one-pot enzymatic synthesis of TMK and ACK. The products were analyzed by HPLC and ESI/MS, which showed peaks at m/z = 563 and 565 for TDP-d-glucose and UDP-d-glucose, respectively, in negative mode.  相似文献   

19.
(1) The ability to produce cephalodia is usually a genus-specific character in lichens. (2)Lecidea shushanii Thoms., is a member of the genusTephromela, closely related toT. aglaea. It is not clear, whether or not the cephalodia of this taxon are true cephalodia or colonies of epiphytic cyanobacteria and whether or notLecidea shushanii is an independent species. (3)Lecidea dovrensis Nyl., is, in contrast to the traditional concept, not conspecific withLecidea alpestris Sommerf., but an earlier name forLecidea pallida Th. Fr. (4)Lecidea dovrensis is described in some detail. Chemically the species is characterized by the presence of isousnic acid (previously unknown in lecideoid lichens). It is restricted to areas north of the 60th parallel with an oceanic climate. (5) In connection with the attempt to clarify the taxonomic relationships ofLecidea dovrensis, figures of ascus apical structures of the following species are given (marked by an asterisk are genera where we found discrepancies with published data):Austrolecia antarctica, Catillaria chalybeia, Lecidea alpestris, L. caesioatra, L. limosa, Lecidoma demissum, Koerberiella wimmeriana, Micarea assimilata, M. crassipes, M. melaenida, M. prasina, Pilophorus robustus, Placodiella olivacea, Placolecis opaca, Porpidia trullisata, Protoblastenia rupestris, Psilolechia lucida, Psorula rufonigra, Squamarina gypsacea, Xanthopsorella texana. (6) Among crustaceous lichens we find no groups related toLecidea dovrensis. We supportTimal's concept of including this species in the genusPilophorus. Pilophorus, as well asLecidea dovrensis is characterized by the same ascus type, by a similar structure of thallus, cephalodia, paraphyses, and ascocarp (although there is no pseudopodetium developed inLecidea dovrensis), and the presence of isousnic acid. In addition, both taxa are restricted to cool oceanic climates and non-calciferous substrates. The following combination is proposed:Pilophorus dovrensis (Nyl.)Timdal, Hertel & Rambold, comb. nova. (7) The species of theLecidea alpestris-group form an independent genus, probably near toAustrolecia Hertel.
Frau Prof. Dr.Elisabeth Tschermak-Woess zu ihrem 70. Geburtstag gewidmet.  相似文献   

20.
The tribePlucheeae (Benth.)A. Anderb., has been analysed cladistically by means of a computerized parsimony program (Hennig 86), using theArctotideae as outgroup. The results of the analysis are presented in a consensus tree and one cladogram. Four major monophyletic subgroups can be recognized: TheColeocoma group (3 genera), thePterocaulon group (3 genera), theLaggera group (6 genera), and thePluchea group (12 genera). All recognized genera are described and most genera are supplied with taxonomical notes including comments on their taxonomic status. Genera such asBlumea, Pluchea, andEpaltes are demonstrated to be unnatural assemblages.Monarrhenus andTessaria are both closely related to thePluchea complex. The old generic nameLitogyne Harv. has been taken up for one species ofEpaltes, the genusRhodogeron is reduced to a synonym ofSachsia, and the following new combinations are made;Litogyne gariepina (DC.)A. Anderb., andSachsia coronopifolia (Griseb.)A. Anderb.  相似文献   

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