Search results for "phosphate"

O-Ribosyl-phosphate purine as a constant modified nucleotide located at position 64 in cytoplasmic initiator tRNAsMetof yeasts

1991

The unknown modified nucleotide G*, isolated from both Schizosaccharomyces pombe and Torulopsis utilis initiator tRNAs(Met), has been identified as an O-ribosyl-(1"----2')-guanosine-5"-phosphate, called Gr(p), by means of HPLC, UV-absorption, mass spectrometry and periodate oxidation procedures. By comparison with the previously published structure of Ar(p) isolated from Saccharomyces cerevisiae initiator tRNA(Met), the (1"----2')-glycosidic bond in Gr(p) has been postulated to have a beta-spatial conformation. The modified nucleotide Gr(p) is located at position 64 in the tRNA(Met) molecules, i.e. at the same position as Ar(p). Since we have also characterized Gr(p) in Candida albicans ini…

Interaction of Oxygen Partial Pressure and Energy Metabolism with the Relaxation Rate of Inorganic Phosphate: A 31P NMR Study

1990

It is well known that oxygen molecules present in liquid or solid samples can shorten NMR spin-lattice relaxation times (T1) of the nucleus under investigation. Several studies have shown large decrements of 1H, 13C, and 19F relaxation times mediated by the O2 molecule (Lees and Muller, 1961; Ohuchi et al., 1979; Fishman et al., 1989). The positions of the 3lp atoms in phosphate compounds are stereometrically similar to some 13C atoms in organic compounds, and thus an effect of oxygen on the 31P T1 is expected. Recently, we have shown (Okunieff et al., 1988) that oxygen breathing can significantly reduce the T1 of 31p in the inorganic phosphate molecule (Pi). The degree to which this change…

Effect of Glufosinate (Phosphinothricin) and Inhibitors of Photorespiration on Photosynthesis and Ribulose-1,5-Bisphosphate Carboxylase Activity

1992

Summary Glufosinate (phosphinothricin) irreversibly inhibits glutamine synthetase and leads to a great decrease in the amino acids glutamine, glutamate, aspartate, serine, glycine and alanine. Due to the lack of glutamate and serine, the transamination of glyoxylate into glycine in the course of photorespiration cannot take place. The inhibition of this part of the photorespiratory process plays the essential role with respect to the photosynthesis inhibition caused by PPT under atmospheric conditions. After addition of different photorespiration or Calvin cycle intermediates to phosphinothricin no decrease in photosynthesis inhibition can be measured. This suggests that photosynthesis inhi…

Selenoproteins, cholesterol-lowering drugs, and the consequences: revisiting of the mevalonate pathway.

2004

3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) and peroxisome proliferator-activated receptor alpha activators (fibrates) are the backbone of pharmacologic hypercholesterolemia and dyslipidemia treatment. Many of their clinical effects, however, are still enigmatic. This article describes how a side road of the mevalonate pathway, characterized in recent years, can rationalize a major fraction of these unexplained observations. This side road is the enzymatic isopentenylation of selenocysteine-tRNA([Ser]Sec) (Sec-tRNA), the singular tRNA to decode the unusual amino acid selenocysteine. The functionally indispensable isopentenylation of Sec-tRNA requires a unique interm…

Differential function of the phosphoglucomutase isozymes PGM1 and PGM2

1979

A total of 13 metabolites thought to be possibly inhibitory were tested for their influence on PGM isozyme activities, each at several different concentrations. The analysis of statistical significance was based on enzyme activities obtained by densitometric measurements of starch gels. Five of the substances were found to inhibit PGM activity, three of which definitely and a further one probably led to a significantly stronger inhibition of the isozymes of the PGM2 locus than of PGM1 isozymes. They are (1) fructose-1,6-diphosphate, (2) adenosine triphosphate, (3) citrate, and (4) possibly 2,3-diphosphoglycerate. Thus, PGM1 isozymes proved to function better in hard or perhaps marginal meta…

Consecutive Selective Adsorption of Pentamidine and Phosphate Biomolecules on a Self-Assembled Layer:  Reversible Formation of a Chemically Selective…

1996

In situ ellipsometric film thickness measurements, FT-IR external reflectance spectroscopy, and potentiometric measurements indicated that the amphiphile pentamidine (PAM), a bisbenzamidine, associated by self-assembly with a preformed self-assembled monolayer of a mercaptoalkanoic acid on gold. The structural properties of PAM and the nature of the substrate were ideal for the formation of a densely packed monolayer. This process was fully reversible, as demonstrated by changing the pH of the surrounding medium. Thus, disassembly−reassembly occurred when the pH was cycled between 8.7 and 3. The bilayer structure, featuring a positively charged amidinium surface, was subsequently used for s…

Bioactivation of the Fungal Phytotoxin 2,5-Anhydro-D-glucitol by Glycolytic Enzymesisan Essential Component of itsMechanism of Action

2002

An isolate of Fusarium solani, NRRL 18883, produces the natural phytotoxin 2,5-anhydro-ᴅ-glucitol (AhG). This fungal metabolite inhibited the growth of roots (I50 of 1.6 mᴍ), butit did nothave any in vitro inhibitory activity. The mechanism of action of AhG requires enzymatic phosphorylation by plant glycolytic kinases to yield AhG-1,6-bisphosphate (AhG-1,6- bisP), an inhibitor of Fru-1,6-bisP aldolase. AhG-1,6-bisP had an I50 value of 570 μᴍ on aldolase activity, and it competed with Fru-1,6-bisP for the catalytic site on the enzyme, with a Ki value of 103 μᴍ. The hydroxyl group on the anomeric carbon of Fru-1,6-bisP is required for the formation of an essential covalent bond to ζ amino fu…

A novel ?-N-cyanate-bridged nickel dinier exhibiting ferromagnetic coupling: Di-?-cyanate-bis(aqua-2,2?:6?,2?-terpyridine)dinickel(II) hexafluorophos…

1986

Tritopic phenanthroline and pyridine tail-tied aza-scorpiands

2010

The synthesis of two new tritopic double-scorpiand receptors in which two equivalent 5-(2-aminoethyl)-2,5,8-triaza[9]-(2,6)-pyridinophane moieties have been linked with 2,6-dimethylpyridine (L1) or 2,9-dimethylphenanthroline (L2) units is reported for the first time. Their acid-base behaviour and Zn(2+) coordination chemistry have been studied by pH-metric titrations, molecular dynamic calculations, NMR, UV-Vis and steady-state fluorescence techniques. L1 and L2 behave, respectively, as hexaprotic and heptaprotic bases in the experimental conditions used (298.1 +/- 0.1 K, 0.15 mol dm(-3) NaCl, pH range under study 2.0-11.0). These ligands are able to form mono-, bi- and trinuclear Zn(2+) co…

Synthesis and characterization of mono- and binuclear copper(II) complexes with 2,2′:6′,2″-terpyridine (terpy) and carboxylates: X-ray crystal struct…

1987

Abstract Perchlorate and hexafluorophosphate salts of monomeric [Cu(terpy)(OOCH)(OH2)]+ and dimeric [Cu(terpy)(OOCR)]22+ cations (terpy = 2,2′:6′,2″-terpyridine, R = CH3 or C2H5) have been synthesized and characterized by IR, electronic and ESR spectra, and analytical data. Spectroscopic results indicate a five-coordinate, close-to-square pyramidal geometry around the copper(II) ion. The half-field absorption in the ΔMs = 2 region of powdered X-band ESR spectra has been observed for the dimeric species. The crystal structure of [Cu(terpy)(OOCH)(OH2)](ClO4) has been determined by X-ray diffraction methods. The compound crystallizes in the space group P21/c with unit-cell dimensions: a = 7.34…