L Heide

..However, recrudescence rates were high in the Artemisia groups. Therefore, monotherapy with Artemisia annua L. cannot be recommended as alternative to modern antimalarials, but may deserve further investigation...

..In fungi, a group of closely related indole prenyltransferase was found to carry out aromatic prenylations with different substrate specificity and regiospecificity, and to catalyze both regular and reverse prenylations...

..If this assumption is true, this study presents the first experiment in combinatorial biosynthesis that uses a halogenase that acts on an acyl carrier protein-bound substrate...

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..CloQ and the similar NovQ from the novobiocin producer seem to belong to a new class of prenyltransferases...

..Their inhibitory activity on gyrase in vitro as well as their antibacterial activity was determined. These results give further insight into the structure-activity relationships of aminocoumarins...

..RT-PCR experiments showed that expression of novG was detectable in the absence of NovE, and also that expression of novE occurred in absence of NovG...

..spheroides was expressed in the couN3 (-) mutant. This led to the formation of bis-carbamoylated coumermycin D, a novel compound of the coumermycin series...

..From these findings it appears that clorobiocin represents a "highly evolved" structure optimized for bacterial transport and DNA gyrase inhibition...

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..Attachment at 4-OH resulted in the highest antibacterial activity. This is the first time that an aminocoumarin antibiotic acylated at 4-OH in noviose has been detected...

..The identities of the new compounds were verified by LC-MS, and their antibacterial activities were tested against Bacillus subtilis in an agar diffusion assay...

..The consensus sequence for the StrR and the putative NovG binding sites was GTTCRACTG(N)(11)CRGTYGAAC. Therefore, NovG and StrR apparently belong to the same family of DNA-binding regulatory proteins...

..Heterologous expression of a key enzyme of novobiocin biosynthesis, i.e., novobiocic acid synthetase, in Streptomyces lividans TK24 further confirmed the involvement of the analyzed genes in the biosynthesis of the antibiotic...

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..Some new compounds were discovered, including bis-carbamoylated novobiocin, hydroxylated clorobiocin, and several structurally and not yet fully elucidated coumermycin derivatives or precursors...

..Structural investigation of the resulting deoxysugars confirmed that both the endogeneous and the heterologous pathway involve a 3,5-epimerization of the deoxysugar, a hypothesis which had recently been questioned...

..Declovanillobiocin lacks the chlorine atom at the aminocoumarin ring. All three compounds had lower antibiotic activity against Bacillus subtilis than clorobiocin...

..The present finding extends the substrate range of this family, previously limited to phenolic compounds, to include also phenazine derivatives...

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..The new, demethylated secondary metabolites were produced in an amount at least as high as that of coumermycin A(1) in the wild-type...

..Expression of these genes in S. lividans TK24 resulted in moderate levels of resistance against novobiocin and coumermycin A(1), suggesting that these genes may be involved in antibiotic transport...

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..The reaction catalyzed by CloR represents a new pathway for the formation of benzoic acids in nature...

..Comparison of the antibacterial activity of clorobiocin analogs with -Cl, -H, or -CH(3) at C-8' showed that chlorine leads to 8-fold higher activity than hydrogen and to 2-fold higher activity than a methyl group...

..Both compounds were isolated on a preparative scale, their structures were elucidated by 1H-NMR and mass spectroscopy and their antibacterial activity was assayed...

..Twenty-five aminocoumarin compounds were prepared by these methods, and their structures were elucidated with mass and 1H-NMR spectroscopy...

..A mechanism for the methylation/acyl transfer process in the late steps of clorobiocin biosynthesis, involving CloN1, CloN2, CloN5, CloN6 and CloN7 is suggested...

..Several compounds showed high levels of activity against staphylococci, including a methicillin-resistant Staphylococcus aureus strain. However, they showed only poor activities against gram-negative strains...

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..Furthermore, they indicate that the C-methylation at position 5 of the pyrrole moiety occurs after the attachment of pyrrole-2-carboxylic acid unit to the deoxysugar moiety...

..In contrast, pyridine carboxylic acids were not accepted. 3-Dimethylallyl-4-hydroxybenzoic acid, the acyl component in novobiocin biosynthesis, was well accepted, despite its structural difference from the genuine acyl substrate of CouL...

..However, when the gyrase inhibitor novobiocin accumulates in the cultures, gyrB(R) is transcribed from its own promoter. Previous work has suggested that this promoter is controlled by the superhelical density of chromosomal DNA...

..Therefore, the enzymes of this family represent attractive tools for the chemoenzymatic synthesis of bioactive molecules...

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..e. an unusual "reverse" prenylation. With 1,3-dihydroxynaphthalene and 4-hydroxybenzoate as substrates Fnq26 catalyzes O-prenylations...

..The possible biosynthetic origin of these moieties is discussed...

..Therefore, the tcp830 promoter presents a robust, easy-to-use system for the inducible expression of biosynthetic gene clusters in heterologous hosts, independent from the genuine regulatory network...

..Two SAM-dependent methyltransferases are encoded within the cluster. Inactivation experiments showed that fnq9 is responsible for the 7-O-methylation and fnq27 for the 6-C-methylation reaction in FNQ I biosynthesis...

..The results give further insight into the structure-activity relationships of aminocoumarin antibiotics...

..This resulted in the formation of 32 new aminocoumarin compounds. The structures of these compounds were elucidated using FAB-MS and (1)H-NMR spectroscopy...

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..Feeding of the mutant with the aminocoumarin moiety of novobiocin led to a new, artificial simocyclinone derivative...

..This is believed to represent the first topo IV identified in the class of actinobacteria, and the first demonstration of the formation of a topo IV as a resistance mechanism of an antibiotic producer...

..A possible mechanism for the role of these three proteins in the acyl-transfer process is suggested...

..Artemisinin plasma concentrations after intake of this herbal tea are sufficient for clinical effects, but insufficient to recommend such preparations as equivalent substitutes for modern artemisinin drugs in malaria therapy...

..These findings make SimL a possible tool for the creation of new aminocoumarin antibiotics...

..lividans TK24 derivatives were at least five times less productive. This method could also be used to carry out functional investigations. Shortening of the cosmids' inserts showed which genes are essential for antibiotic production...

..These bacterial enzymes catalyze the prenylation of aromatic substrates in the biosynthesis of secondary metabolites (i.e., a reaction similar to that of DMATS)...

..However, detailed investigations of the biosynthesis revealed that the biosynthetic pathway and the enzymes involved are totally different from those identified in plants...

..The genes for these fungal prenyltransferases are not located within recognizable secondary metabolic gene clusters. Their physiological function is yet unknown...

..Shikonin accumulation remained unchanged even upon high expression of soluble HMGR...

..These methods can be combined, allowing the generation of a wide variety of new compounds. This chapter may provide general pointers for the use of genetic methods in the generation of new antibiotics...

..6% Q2-5247 and 0.2 mg l(-1) CoCl(2)). In contrast, heterologous production of caprazamycin derivatives was optimal in strain M1154 (amounts of 152 mg l(-1) on average)...

..Starting from alternative dicarboxy scaffolds, these four enzymes can be utilized in tandem to create additional variants of dimeric aminocoumarin antibiotics...

..This is the first report of a systematic evaluation of a series of aminocoumarins against both gyrase and topo IV. The results give further insight into the structure-activity relationships of aminocoumarin antibiotics...

..6%. CloQ is involved in the biosynthesis of the aminocoumarin antibiotic clorobiocin, which targets the essential bacterial enzyme DNA gyrase...

..NovS reduces the product formed from the reaction of NovW with dTDP-4-keto-6-deoxy-D-glucose in the presence of NADH to result in dTDP-l-rhamnose. Furthermore, a pathway for the biosynthesis of noviose is proposed...

..After seven days, the cure rate was 7/10 for the Aa compared to 7/9 for SP; this dropped to 4/10 for Aa and 4/9 for SP at day 14 and to 1/9 for Aa and 3/8 for SP at day 28...

..The described method may be utilised for the characterisation of herbal medicines in order to ensure comparability of medication in further clinical trials...

..The incorporation pattern of [2-13C]glycerol was consistent with a "reverse" prenyl transfer, that is, with the formation of a C-C bond from C-3 of GPP to the polyketide nucleus of FNQ I...

..This is a novel mechanism for a gyrase inhibitor and presents new possibilities for antibacterial drug development...

..It is predicted to perform two consecutive oxidative decarboxylation steps in the biosynthesis of the prenylated hydroxybenzoic acid moiety of the aminocoumarin antibiotic novobiocin...