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At least 379 records · Page 21Linked to original sources
PubMed1966

5-Dehydroshikimate reductase in the tea plant (Camellia sinensis L.). Properties and distribution.

1. A method for the extraction of 5-dehydroshikimate reductase (EC 1.1.1.25) from tea plant tissues in an active soluble state has been developed. It is dependent on the use, in the extraction medium, of an insoluble polyphenol adsorbent (Polyclar AT), which prevents the polyphenols present from precipitating all the proteins. 2. The enzyme has the following properties: pH optima at pH10.1 in glycine-sodium hydroxide buffer and at pH7.7 in tris-hydrochloric acid buffer; K(m) (NADP) 32mum and K(m) (shikimate) 0.43mm; and NADP-specificity. It was completely inhibited by 0.33mm-p-chloromercuribenzoate and this inhibition was completely reversed by 10mm-cysteine. Iodoacetate and arsenite inhibited the enzyme to a smaller extent. 3. The specific activity of the enzyme was higher in the parts of the actively growing shoot tips (third leaf>stem>second leaf>first leaf>bud) than in the mature leaves. However, the mature leaves had the greatest total activity. 4. The importance of these findings with respect to flavanol biosynthesis in tea plants is discussed.

Alcohol Oxidoreductases↗
PubMed1995

Ubiquinone biosynthesis in Leishmania major promastigotes.

Promastigotes of Leishmania major contain a ubiquinone which has a side chain made up of nine isoprene subunits (UQ9). Incorporation of radioactivity from [14C] acetate and [14C] mevalonate into ubiquinone as well as the identification of hydroxymethylglutaryl coenzyme A reductase (HMG CoA reductase), and mevalonate kinase indicate that the isoprenoid portion of the molecule is synthesized by the acetate-mevalonate pathway as in mammalian cells. Incorporation of [14C] tyrosine into ubiquinone is low, but [14C] parahydroxybenzoic acid is readily incorporated. Distribution of radioactivity from [14C] acetate indicates that about 60-80% is associated with the side chain and about 20% with the ring. Label from parahydroxybenzoic acid is, however, incorporated preferentially into the ring. L. major is capable of synthesizing the aromatic ring of ubiquinone from acetate, parahydroxybenzoate being an important intermediate. In this behaviour it resembles procaryotes. Ubiquinone biosynthetic pathway in L. major thus shares characteristics with mammalian and bacterial systems.

Acetates↗
PubMed2000

Synthesis of gallic acid: Cu(2+)-mediated oxidation of 3-dehydroshikimic acid.

With the elaboration of high-yielding, high-titer syntheses of 3-dehydroshikimic acid from glucose using recombinant Escherichia coli, oxidation of this hydroaromatic becomes a potential route for synthesis of gallic acid. Conversion of 3-dehydroshikimic acid into gallic acid likely proceeds via initial enolization of an alpha-hydroxycarbonyl and oxidation of the resulting enediol. 3-Dehydroshikimate enolization in water was catalyzed by inorganic phosphate while Zn(2+) was used to catalyze enolization in acetic acid. Enediol oxidation employed Cu(2+) as either the stoichiometric oxidant or as a catalyst in the presence of a cooxidant. Gallic acid was produced in a yield of 36% when 3-dehydroshikimic acid in phosphate-buffered water reacted for 35 h with H2O2 and catalytic amounts of CuSO(4). 3-Dehydroshikimate-containing, phosphate-buffered culture supernatants reacted with stoichiometric amounts of CuCO(3)Cu(OH)(2) and Cu(x)(H(3-x)(PO4)(2) to give gallic acid in yields of 51% in 5 h and 43% in 12 h, respectively. Solutions of 3-dehydroshikimic acid in acetic acid reacted with stoichiometric amounts of Cu(OAc)(2) to afford a 74% yield of gallic acid in 36 h. Acetic acid solutions of 3-dehydroshikimic acid could also be oxidized by air using catalytic quantities of Cu(OAc)(2). ZnO accelerated these oxidations leading to a 67% yield of gallic acid in 4 h when an acetic acid solution of 3-dehydroshikimic acid was reacted with O(2) and a catalytic amount of Cu(OAc)(2).

Catalysis↗
PubMed1984

A radiometric assay for 5-enolpyruvylshikimate-3-phosphate synthase.

A new assay for 5-enolpyruvylshikimate-3-phosphate synthase is described. This enzyme of the shikimate pathway of aromatic amino acid biosynthesis generates 5-enolpyruvylshikimate 3-phosphate and orthophosphate from phosphoenolpyruvate and shikimate 3-phosphate. The shikimate pathway is present in bacteria and plants but not in mammals. The assay employs a paper-chromatographic separation of radiolabeled substrate from product. The method is specific, is sensitive to 50 pmol of product, and is suitable for use in crude extracts of bacteria. This enzyme appears to be the primary target site of the commercial herbicide glyphosate (N-phosphonomethyl glycine). A procedure for the enzymatic synthesis of [14C]shikimate 3-phosphate from the commercially available precursor [14C]shikimic acid is also described.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗
PubMed1998

Separation of inorganic and organic anions by capillary zone electrophoresis with simultaneous indirect UV and conductivity detection.

The analysis of low-molecular-mass anionic compounds using capillary zone electrophoresis (CZE) with simultaneous direct conductivity and indirect UV detection is described. A number of carrier electrolyte compositions has been investigated with respect to the crucial parameters for their compatibility with both detection principles discussed in this paper (UV absorptivity and electrophoretic mobility of the buffer coion). Additionally, parameters including pH and buffer concentration affecting both peak symmetry and signal-to-noise ratio obtained for the analytes of interest had to be optimized. Best results could be achieved with a carrier electrolyte consisting of 4-aminobenzoic acid, bis(2-hydroxyethyl)imino-tris(hydroxymethyl)aminomethane (BIS-Tris) and a pH of 7.0 adjusted with LiOH. This running buffer was used for the analysis of low-molecular-mass anionic compounds in a sample of white wine.

4-Aminobenzoic Acid↗
PubMed2005

Effect of the conservation procedure on the contents of phenolic compounds and organic acids in chanterelle (Cantharellus cibarius) mushroom.

To check the influence of the conservation procedure in the chemical composition of chanterelle mushroom, phenolic compounds and organic acids of samples preserved under four different conditions (drying, freezing, conservation in olive oil and in vinegar) were determined. Phenolics and organic acids were analyzed by HPLC-DAD and HPLC-UV, respectively. The results showed that chanterelle is characterized by the presence of six phenolic compounds (3-, 4-, and 5-O-caffeoylquinic acid, caffeic acid, p-coumaric acid, and rutin) and five organic acids (citric, ascorbic, malic, shikimic, and fumaric acids). Samples preserved in olive oil also exhibited hydroxytyrosol, tyrosol, luteolin, and apigenin, whereas conservation in vinegar led to the detection of hydroxytyrosol, tyrosol, and tartaric acid in the analyzed samples. The conservation procedures to which chanterelle samples were subjected seem to affect the qualitative and quantitative phenolics and organic acids profiles.

Acetic Acid↗
PubMed2006

Analysis of the Arabidopsis rsr4-1/pdx1-3 mutant reveals the critical function of the PDX1 protein family in metabolism, development, and vitamin B6 biosynthesis.

Vitamin B6 represents a highly important group of compounds ubiquitous in all living organisms. It has been demonstrated to alleviate oxidative stress and in its phosphorylated form participates as a cofactor in >100 biochemical reactions. By means of a genetic approach, we have identified a novel mutant, rsr4-1 (for reduced sugar response), with aberrant root and leaf growth that requires supplementation of vitamin B6 for normal development. Cloning of the mutated gene revealed that rsr4-1 carries a point mutation in a member of the PDX1/SOR1/SNZ (for Pyridoxine biosynthesis protein 1/Singlet oxygen resistant 1/Snooze) family that leads to reduced vitamin B6 content. Consequently, metabolism is broadly altered, mainly affecting amino acid, raffinose, and shikimate contents and trichloroacetic acid cycle constituents. Yeast two-hybrid and pull-down analyses showed that Arabidopsis thaliana PDX1 proteins can form oligomers. Interestingly, the mutant form of PDX1 has severely reduced capability to oligomerize, potentially suggesting that oligomerization is important for function. In summary, our results demonstrate the critical function of the PDX1 protein family for metabolism, whole-plant development, and vitamin B6 biosynthesis in higher plants.

Amino Acid Sequence↗
PubMed1998

Ultraviolet radiation-absorbing mycosporine-like amino acids (MAAs) are acquired from their diet by medaka fish (Oryzias latipes) but not by SKH-1 hairless mice.

To assess whether vertebrates can acquire, from their diet, ultraviolet radiation-absorbing mycosporine-like amino acids (MAAs), medaka fish and hairless mice were maintained for 150 and 130 days, respectively, on diets either including Mastocarpus stellatus (rich in MAAs) or the same diets without this red alga. In medaka, the MAAs palythine and asterina-330, present in trace quantities in the diet with added M. stellatus, were present in significantly greater quantities in the eyes of fish fed this diet than in the eyes of control fish. Only traces of MAAs were present in the skin of medaka fed the diet containing MAAs. Shinorine, the principal MAA in M. stellatus, was not found in any tissues of medaka, which raises questions about the specificity of transport of MAAs. In hairless mice, no dietary MAAs were found in the tissues of the eyes, skin, or liver after maintenance on the experimental diet. Low concentrations of shinorine were present only in the tissues of the small and large intestines. These results indicate that MAAs are acquired from their diet and translocated to superficial tissues by teleost fish, but that mammals may be incapable of such. Thus, dietary supplementation with MAAs may be useful in aquacultured species of fish, but MAAs as 'dietary sunscreens' may not be an option for mammals, including humans. Nevertheless, our demonstration of the uptake of shinorine by human skin cancer cells in culture raises evolutionary questions regarding the organ specificity of the capacity for the cellular transport of MAAs.

Absorption↗