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51.
Zhu YF Wang XC Connors P Wilcoxen K Gao Y Gross R Strack N Gross T McCarthy JR Xie Q Ling N Chen C 《Bioorganic & medicinal chemistry letters》2003,13(11):1931-1934
4-benzylquinolines 5, based on a series of isoquinolines 1, were prepared and tested as inhibitors of the IGF/IGFBP-3 complex based on their ability to displace IGF-I from its binding to IGF-binding protein-3. SAR studies on the 6,7-dihydroxy moiety of the quinoline 5a showed that the catecol moiety could be replaced with other functional groups. Computational modeling of the 5a/mini-IGFBP-5 complex revealed the possible binding site of 5a on IGFBP-5. 相似文献
52.
The control of malate metabolism and stimulation of 1-sinapolyglucose: L-malate sinapoyltransferase (SMT) activity in radish (Raphanus sativus L. var. sativus) cotyledons has been studied. The light-induced and nitrate-dependent activity of SMT catalyzes the formation of O-sinapoly-L-malate via 1-O-sinapoyl--D-glucose. When dark-grown radish seedlings, cultivated in quartz sand with nutrient solution containing NO
3
-
as the sole N source, were treated with light, SMT activity increased concomitantly with free malate in the cotyledons. This light effect was suppressed in seedlings grown in a culture medium which contained in addition to NO
3
-
also NH
4
+
. However, treatment with methionine sulfoximine neutralized this ammonium effect, resulting again in both rapid accumulation of malate and rapid increase in SMT activity. When seedlings grown on NO
3
-
nitrogen were subsequently supplied with NH
4
+
nitrogen, the accumulated level of L-malate rapidly dropped and the SMT increase ceased. The enzyme activity decreased later on, reaching the low activity level of plants which were grown permanently on NO
3
-
/NH
4
+
-nitrogen. An external supply (vacuum infiltration) of malate to excised cotyledons and intact seedings, grown on NO
3
-
/NH
4
+
-nitrogen medium, specifically promoted a dose-dependent increase in the activity of SMT. In summary these results provide evidence indicating that the SMT activity in cotyledons of Raphanus sativus might be related to the metabolism of malic acid.Abbreviation MSO
L-methionine sulfoximine
- SinGlc
1-O-sinapoyl--D-glucose
- SinMal
O-sinapoyl-L-malate
- SMT
1-O-sinapoyl--D-glucose:L-malate sinapolytransferase 相似文献
53.
Protein preparations from seeds and seedlings (cotyledons) of rape (Brassica napus subsp. napus [L.] DC.) catalyzed the transfer of sinapic acid from 1-Osinapoyl--glucose to malate in the formation of O-s-inapoylmalate. The enzyme involved, 1-O-sinapoyl--glucose: l-malate O-sinapoyltransferase (SMT; EC 2.3.1), catalyzes the key step in the overall conversion of the seed constituent sinapine (O-sinapoylcholine) to the accumulating O-sinapoylmalate by way of the intermediate 1-O-sinapoyl--glucose. The present paper describes this phenomenon focussing on SMT activity.Abbreviations Sin-Glc
1-O-sinapoyl--glucose
- Sin-Mal
O-sinapoylmalate
- SMT
1-O-sinapoyl--glucose: l-malate sinapoyltransferase (EC 2.3.1)
This work was supported by the Deutsche Forschungsgemeinschaft, the Fonds der Chemischen Industrie and the Ontario Ministry of Agriculture and Food. 相似文献
54.
The distribution of l-malate, sinapic acid esters and 1-sinapoylglucose: l-malate sinapoyltransferase (SMT) which catalyzes the synthesis of sinapoyl-l-malate were examined in preparations of protoplasts obtained from cotyledons of red radish (Raphanus sativus L. var. sativus). Vacuoles isolated from the protoplasts contained all of the SMT activity, all of the accumulated sinapic acid esters and about 50% of free l-malate present initially in the protoplasts. An esterase activity, acting on 1-sinapoyglucose, was found to be exclusively localized in the cytoplasm and a large proportion was found to be recoverable in a 100 000-g pellet obtained from protoplast lysates. The vacuoles were obtained after lysis of the protoplasts by osmotic shock and purification on a Ficoll gradient. The cytoplasmic contamination of vacuole preparations was found to be about 10%, as judged by enzymatic markers and microscopic inspection. No SMT activity was found in a 100 000-g pellet obtained from vacuole lysates. The results indicate that biosynthesis of sinapoyl-l-malate takes place within the central vacuoles of redradish cotyledons.Abbreviation SMT
1-sinapoylglucose: l-malate sinapol-transferase 相似文献
55.
Mutations of basic amino acids of NCp7 of human immunodeficiency virus type 1 affect RNA binding in vitro. 总被引:8,自引:7,他引:1
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The nucleocapsid (NC) protein of human immunodeficiency virus type 1 is required for packaging of viral RNA and for virion assembly. It contains two clusters of basic amino acids, consisting of five and four amino acid residues, flanking the first of its two zinc fingers. These amino acid residues have been mutagenized to neutral ones individually, as well as in various combinations, by site-directed mutagenesis. Wild-type NCp7 and the mutant proteins were expressed as recombinant proteins in Escherichia coli, with six histidines as tags at their amino termini in order to allow efficient purification. The purified proteins were analyzed for RNA binding in vitro with human immunodeficiency virus type 1 5' leader RNA transcribed in vitro. Assays comprised Northwestern blots at various salt concentrations and filter binding tests which allowed determination of the dissociation constants of the various mutants. The results indicated that mutations of the amino acid R-7 and of R-32 and K-33 were more critical for RNA binding than other mutations. Mutation of the other amino acid residues reduced the binding affinity in proportion to the number of mutations. Mutation of seven of the nine basic amino acid residues reduced the binding of RNA by 50- to 90-fold. 相似文献
56.
Accumulation of sesquiterpenoid cyclohexenone derivatives induced by an arbuscular mycorrhizal fungus in members of the Poaceae 总被引:7,自引:0,他引:7
Sixty one members of the Poaceae, including various cereals, were grown in defined nutrient media with and without the arbuscular
mycorrhizal (AM) fungus, Glomus intraradices Schenk & Smith. The roots of all species investigated were colonized by the AM fungus, however, to different degrees and
independent of their systematic position. High-performance liquid chromatographic analyses of methanolic extracts from the
roots of mycorrhizal and nonmycorrhizal species revealed dramatic changes in the patterns of UV-detectable products along
with a widespread occurrence of AM-fungus-induced accumulation of sesquiterpenoid cyclohexenone derivatives. The latter occur
most often in the tribes Poeae, Triticeae and Aveneae. Some additional control experiments on plant infection with pathogens
(Gaeumannomyces graminis) and Drechslera sp.) or an endophyte (Fusarium sp.), as well as application of abiotic stress, proved that the metabolism of these terpenoids is part of a response pattern
of many gramineous roots in their specific reaction to AM fungal colonization.
Received: 23 October 1996 / Accepted 11 December 1996 相似文献
57.
Uridine 5′-diphosphoglucose:betanidin 5-O- and 6-O-glucosyltransferases (5-GT and 6-GT; EC 2.4.1) catalyze the regiospecific formation of betanin (betanidin 5-O-β-glucoside) and gomphrenin I (betanidin 6-O-β-glucoside), respectively. Both enzymes were purified to near homogeneity from cell-suspension cultures of Dorotheanthus bellidiformis, the 5-GT by classical chromatographic techniques and the 6-GT by affinity dye-ligand chromatography using UDP-glucose as
eluent. Data obtained with highly purified enzymes indicate that 5-GT and 6-GT catalyze the indiscriminate transfer of glucose
from UDP-glucose to hydroxyl groups of betanidin, flavonols, anthocyanidins and flavones, but discriminate between individual
hydroxyl groups of the respective acceptor compounds. The 5-GT catalyzes the transfer of glucose to the C-4′ hydroxyl group
of quercetin as its best substrate, and the 6-GT to the C-3 hydroxyl group of cyanidin as its best substrate. Both enzymes
also catalyze the formation of the respective 7-O-glucosides, but to a minor extent. Although the enzymes were not isolated to homogeneity, chromatographic, electrophoretic
and kinetic properties proved that the respective enzyme activities were based on the presence of single enzymes, i.e. 5-GT
and 6-GT. The N terminus of the 6-GT revealed high sequence identity to a proposed UDP-glucose:flavonol 3-O-glucosyltransferase (UF3GT) of Manihot esculenta. In addition to the 5-GT and 6-GT, we isolated a UF3GT from D. bellidiformis cell cultures that preferentially accepted myricetin and quercetin, but was inactive with betanidin. The same result was
obtained with a UF3GT from Antirrhinum majus and a flavonol 4′-O-glucosyltransferase from Allium cepa. Based on these results, the main question to be addressed reads: Are the characteristics of the 5-GT and 6-GT indicative
of their phylogenetic relationship with flavonoid glucosyltransferases?
Received: 11 February 1997 / Accepted: 18 April 1997 相似文献
58.
Cell-suspension cultures ofChenopodium rubrum accumulate various soluble secondary phenolic metabolites such as the hydroxybenzoic acid glycosides 4-hydroxybenzoic acid--glucoside, vanillic acid--glucoside, the hydroxycinnamic acid acylglycosides 1-O-(4-coumaroyl)--glucose, 1-O-feruloyl--glucose, 1-O-sinapoyl--glucose and 1-O-feruloyl-(-1,2-glucuronosyl)--glucose, the hydroxycinnamic acid amide N-feruloylaspartate, and the betacyanins betanin, amaranthin and celosianin II. In addition, accumulation of the insoluble cell wall-bound hydroxycinnamic acids with ferulic acid as the major component occurs parallel to culture growth. The changes of three pivotal enzymatic activities, all O-transferases which are involved in the formation of the dominant ferulic acid conjugates, were determined. These are (i) uridine 5-diphosphate(UDP)glucose-hydroxycinnamic acid O-glucosyltransferase (EC 2.4.1), (ii) UDP-glucuronic acid:1-O-hydroxycin-namoyl--glucose O-glucuronosyltransferase (EC 2.4.1) and (iii) 1-O-hydroxycinnamoyl--glucose:amaranthin O-hydroxycinnamoyltransferase (EC 2.3.1). The patterns of metabolite accumulation associated with these enzyme activities show that the hydroxycinnamic acid-glucose esters play a central role as metabolically active intermediates in the secondary metabolism ofCh. rubrum. Two cell lines of this culture (CH, CHN), differing in their betacyanin content, were compared with respect to this metabolism. A markedly higher total betacyanin content in the CHN line might possibly be the consequence of an increased supply of the key precursor for betalain biosynthesis, i.e. 3,4-dihydroxyphenylalanine (DOPA). In addition, the enhanced accumulation of celosianin II in the CHN line correlates well with a higher activity of the enzyme catalyzing the transfer of ferulic acid from 1-O-feruloyl--glucose to amaranthin.Abbreviations CH line
red-coloured betalain-producing cell-suspension cultures ofChenopodium rubrum (lower betacyanin content)
- CHN line
deep-red-coloured betalain-producing cell-suspension cultures ofCh. rubrum (higher betacyanin content), selected from CH line
- DOPA
3,4-dihydroxyphenylalanine
- glucosyltransferase
uridine 5-diphosphate-glucose hydroxycinnamic acid O-glucosyltransferase (EC 2.4.1)
- glucuronosyltransferase
uridine 5-diphosphate-glucuronic acid: 1-O-hydroxycinnamoyl--glucose O-glucuronosyltransferase (EC 2.4.1)
- HPLC
high-performance liquid chromatography
- hydroxycinnamoyltransferase
1-O-hydroxycinnamoyl--glucose:amaranthin O-hydroxycinnamoyltransferase (EC 2.3.1)
- NMR
nuclear magnetic resonance
Support by the Deutsche Forschungsgemeinschaft and by the Fonds der Chemischen Industrie to D.S. is gratefully acknowledged. We thank Sabine Fehling for help in cell wall analyses and Heike Steingaß for optimization of enzyme assays. Our special thanks are due to Dr H. Harms (FAL, Braunschweig, FRG) and Dr J. Berlin (BBA, Braunschweig) for establishing and providing the CH and CHN lines, respectively, of theChenopodium rubrum cell culture. We are grateful to Christel Kokoschka, H. Dirks and Inge Schweer (GBF, Braunschweig) for recording the NMR, FAB MS and EI MS data, respectively. 相似文献
59.
The nucleotide sequence of the relaxase operon and the leader operon which are part of the Tra1 region of the promiscuous plasmid RP4 was determined. These two polycistronic operons are transcribed divergently from an intergenic region of about 360 bp containing the transfer origin and six close-packed genes. A seventh gene completely overlaps another one in a different reading frame. Conjugative DNA transfer proceeds unidirectionally from oriT with the leader operon heading the DNA to be transferred. The traI gene of the relaxase operon includes within its 3' terminal region a promoter controlling the 7.2-kb polycistronic primase operon. Comparative sequence analysis of the closely related IncP plasmid R751 revealed a similarity of 74% at the nucleotide sequence level, indicating that RP4 and R751 have evolved from a common ancestor. The gene organization of relaxase- and leader operons is conserved among the two IncP plasmids. The transfer origins and the genes traJ and traK exhibit greater sequence divergence than the other genes of the corresponding operons. This is conceivable, because traJ and traK are specificity determinants, the products of which can only recognize homologous oriT sequences. Surprisingly, the organization of the IncP relaxase operons resembles that of the virD operon of Agrobacterium tumefaciens plasmid pTiA6 that mediates DNA transfer to plant cells by a process analogous to bacterial conjugation. Furthermore, the IncP TraG proteins and the product of the virD4 gene share extended amino acid sequence similarity, suggesting a functional relationship. 相似文献
60.
Seedlings of red radish (Raphanus sativus L. var. sativus) accumulated high amounts of free malic acid and sinapoylmalate, when grown on nitrate as the sole N-source. In the presence of ammonium (NO
3
–
: NH
4
+
, 1:2) both metabolites failed to accumulate, and the levels of arginine, asparagine, glutamine, histidine, and serine were greatly increased. The extractable activity of 1-sinapoylglucose: l-malate sinapoyltransferase, an enzyme which plays a key role in channelling malic acid into the sinapic-acid metabolism of this plant, was positively correlated with the malic-acid level in cotyledons. The possibility is discussed that free malic acid might be the likely candidate for regulating the activity of 1-sinapoylglucose: l-malate sinapoyltransferase.Abbreviation SMT
sinapoylglucose: L-malate sinapoyltransferase 相似文献