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Purification and characterization of 3-dehydroshikimate dehydratase, an enzyme in the inducible quinic acid catabolic pathway of Neurospora crassa.

3-Dehydroshikimate dehydratase catalyzes the third reaction in the inducible quinic acid catabolic pathway of Neurospora crassa and is encoded in the qa-4 gene of the qa gene cluster. As part of continuing genetic and biochemical studies concerning the organization and regulation of this gene cluster, 3-dehydroshikimate dehydratase has been purified and characterized biochemically. The enzyme was purified 1650-fold using the following techniques: 1) (NH4)2SO4 fractionation; 2) ion exchange chromatography on DEAE-cellulose; 3) gel filtration on Sephadex G-100; 4) ion exchange chromatography on Cellex QAE (quaternary aminoethyl); and 5) hydroxylapatite chromatography. 3-Dehydroshikimate dehydratase is a monomer with a molecular weight of about 37,000 and a sedimentation coefficient of 3.27 S. It has a Km value of 5.9 X 10(-4) and an average isoelectric point of 4.92. The purified enzyme is extremely sensitive to thermal denaturation but can be significantly stabilized by Mg2+ ions. The purified enzyme also exhibits maximal catalytic activity only when assayed in the presence of certain divalent cations, e.g. magnesium. The NH2-terminal residue of 3-dehydroshikimate dehydratase is proline, and its alpha-amino group is unblocked.

Amino Acids↗

Bowdenol, a new 2,3-dihydrobenzofuran constituent from Bowdichia virgilioides.

From the stem bark of Bowdichia virgilioides, lupeol, lupeol acetate, sitosterol, stigmasterol and methyl-3-[2-(1-hydroxymethylvinyl)-2,3-dihydrobenzo[b]furan-5-yl]-(E)-2-propenoate have been isolated. The latter is a new compound and it has been named as bowdenol. Their structures were elucidated with the aid of spectroscopic techniques, mostly 1 and 2D NMR. The biogenetic pathway for bowdenol has been suggested.

Acrylates↗

Influence of two fertilization regimens on the amounts of organic acids and phenolic compounds of tronchuda cabbage (Brassica oleracea L. Var. costata DC).

A phytochemical study was undertaken on tronchuda cabbage (Brassica oleracea L. var. costata DC) cultivated under conventional and organic practices and collected at different times. Six organic acids (aconitic, citric, ascorbic, malic, shikimic, and fumaric acids) were identified and quantified by HPLC-UV. Qualitative and quantitative differences were noted between internal and external leaves. Analysis of the phenolics of the internal leaves was achieved by HPLC-DAD, and the phenolic profile obtained was revealed to be distinct from that of the external leaves. By this means were identified and quantified 11 compounds: 3-p-coumaroylquinic acid, kaempferol 3-O-sophoroside-7-O-glucoside, kaempferol 3-O-(caffeoyl)sophoroside-7-O-glucoside, kaempferol 3-O-(sinapoyl)sophoroside-7-O-glucoside, kaempferol 3-O-(feruloyl)sophoroside-7-O-glucoside, kaempferol 3-O-sophoroside, two isomeric forms of 1,2-disinapoylgentiobiose, 1-sinapoyl-2-feruloylgentiobiose, 1,2,2'-trisinapoylgentiobiose, and 1,2'-disinapoyl-2-feruloylgentiobiose. In general, internal leaves exhibited more constant chemical profiles.

Agriculture↗

Escherichia coli chorismate synthase: a deuterium kinetic-isotope effect under single-turnover and steady-state conditions shows that a flavin intermediate forms before the C-(6proR)-H bond is cleaved.

We report the observation of a deuterium kinetic isotope effect for the conversion of 5-enolpyruvylshikimate-3-phosphate into chorismate (6proR2HV = 1.13 +/- 0.03) using recombinant chorismate synthase from Escherichia coli. Similar isotope effects were observed for the decay of a spectroscopically characterized flavin intermediate (6proR2Hk = 1.17 +/- 0.04) during single-turnover experiments. The main rate-limiting steps and C-(6proR)-H bond breaking are therefore distinct and both must occur after the formation of the flavin intermediate and either before or concomitant with its decay.

Binding Sites↗

Genetic analysis of phenylalanine-responding mutants of Pseudomonas aeruginosa.

A transduction analysis of phenylalanine-responding mutants of Pseudomonas aeruginosa revealed the existence of six unlinked genes. Enzyme assays showed that one gene was involved in the terminal production of phenylalanine (chorismate mutase), and the remaining five genes were involved in the common pathway of aromatic amino acid biosynthesis.

Cell-Free System↗