26 research outputs found
Phosphorylation of C6- and C3-positions of glucosyl residues in starch is catalysed by distinct dikinases
AbstractGlucan, water dikinase (GWD) and phosphoglucan, water dikinase (PWD) are required for normal starch metabolism. We analysed starch phosphorylation in Arabidopsis wild-type plants and mutants lacking either GWD or PWD using 31P NMR. Phosphorylation at both C6- and C3-positions of glucose moieties in starch was drastically decreased in GWD-deficient mutants. In starch from PWD-deficient plants C3-bound phosphate was reduced to levels close to the detection limit. The latter result contrasts with previous reports according to which GWD phosphorylates both C6- and C3-positions. In these studies, phosphorylation had been analysed by HPLC of acid-hydrolysed glucans. We now show that maltose-6-phosphate, a product of incomplete starch hydrolysis, co-eluted with glucose-3-phosphate under the chromatographic conditions applied. Re-examination of the specificity of the dikinases using an improved method demonstrates that C6- and C3-phosphorylation is selectively catalysed by GWD and PWD, respectively
Alteration of Transthyretin Microheterogeneity in Serum of Multiple Trauma Patients
Transthyretin (TTR) which exists in various isoforms, is a valid marker for acute phase response and subclinical malnutrition. The aim of the study was to investigate the relationship between inflammation, oxidative stress and the occurrence of changes in microheterogeneity of TTR
Front-end-resolution and hadamard transform in Fourier transform ion cyclotron resonance
Matrix-assisted laser desorption/ionization time of flight mass spectrometry peptide mass fingerprints and post source decay: a tool for the identification and analysis of phloem proteins from Cucurbita maxima Duch. separated by two-dimensional polyacrylamide gel electrophoresis
Matrix-assisted laser desorption/ionization time of flight mass spectrometry peptide mass fingerprints and post source decay: a tool for the identification and analysis of phloem proteins from Cucurbita maxima Duch. separated by two-dimensional polyacrylamide gel electrophoresis
Vitamin A excreted in the urine of canines is associated with a Tamm-Horsfall like protein
Under physiological conditions canines transport vitamin A in blood plasma primarily
as retinyl esters bound to lipoproteins and excrete substantial amounts of vitamin A
as retinol and retinyl esters with urine. In the aqueous environment of urine,
the hydrophobic vitamin A has to be associated with a protein. This vitamin A-protein
complex was purified to homogeneity, prepared by preparative ultracentrifugation
(density 1.21 g/mL), native polyacrylamide gel electrophoresis (PAGE) and size
exclusion chromatography. The vitamin A-protein complex has a high molecular mass
of kDa under native conditions. SDS PAGE under reduced conditions revealed a
single band with a molecular mass of about 100 kDa for the protein moiety. Peptides
obtained after limited proteolysis with trypsin from the 100 kDa protein were characterised
by MALDI-TOF mass spectrometry and showed amino acid sequence homology to the human
Tamm-Horsfall Protein (THP). This was further confirmed by a positive immunoreaction
of the isolated protein with crossreacting human THP antibodies. The localisation of
THP in dog kidneys was determined by using immunohistology. The reaction was strong
along the entire thick ascending limb of the Henle loop and distal convoluted tubule.
Our data point to the possibility that THP functions as a novel carrier for vitamin A
in the urine of canines.La vitamine A excrétée dans l'urine des canidés est associée à une protéine homologue
à la Tamm-Horsfall. Dans des conditions physiologiques normales, les canidés transportent
la vitamine A dans le plasma sanguin principalement sous forme de rétinyl esters liés
aux lipoprotéines et excrètent des taux importants de vitamine A sous forme de rétinol
et de rétinyl esters dans l'urine. Dans l'environnement aqueux de l'urine,
la vitamine A hydrophobe doit être associée à une protéine. Ce complexe protéine-vitamine A
a été purifié et homogénéisé, préparé par ultracentrifugation (1,21 g/mL de densité),
électrophorèse sur gel de polyacrylamide natif (PAGE) et chromatographie d'exclusion
de taille. Le complexe protéine-vitamine A a une masse moléculaire élevée supérieure
à 5 000 kDa dans les conditions natives. Le SDS PAGE effectué dans des conditions réduites
a révélé une bande unique avec une masse moléculaire d'environ 100 kDa pour la partie
protéique. Les peptides obtenus à partir de la protéine de 100 kDa, après protéolyse limitée
avec de la trypsine, ont été caractérisés par spectrométrie de masse MALDI-TOF et ont montré
une homologie de séquence en acides aminés avec la protéine Tamm-Horsfall (PTH) humaine.
Ceci a été confirmé par une immuno-réaction positive entre la protéine isolée et les
anticorps présentant une réaction croisée avec la PTH humaine. La localisation de la PTH
dans le rein de chien a été déterminée par immunohistologie. La réaction a été forte tout
le long de la section ascendante épaisse de l'anse de Henle, et du tubule contourné distal.
Nos résultats suggèrent que la PTH fonctionne comme un nouveau transporteur pour la
vitamine A dans l'urine des canidés