1,721,049 research outputs found
Oxidative deamination of epsilon-N-acetylthialysine and epsilon-N-acetylselenalysine by snake venom L-aminoacid oxidase.
No full textepsilon-N-acetylthialysine and epsilon-N-acetylselenalysine are oxidatively deaminated by Crotalus adamanteus l-aminoacid oxidase, giving rise to the corresponding alpha-ketoacids, identified by some chemical and chromatographic tests and by comparison with synthetic compounds. no cleavage of the C-S or C-Se bonds of the substrates occurs during the reaction. The enzyme acts as well on the epsilon-N-acetylderivatives of thialysine and selenalysine as on epsilon-N-acetyllysine. The substitution of the gamma methylene group of lysine by a sulfur or a selenium atom seems not to greatly affect the substrate specificity of the enzyme
Carboxymethyl-selenopyruvic acid as the product of the oxidative deamination of carboxymethyl-selenocysteine
No full text[No abstract available
Oxidative deamination of thialysine by snake venom L-aminoacid oxidase.
No full textThialysine is oxidatively deaminated by snake venom L-aminoacid oxidase at alkaline pH. The oxygen consumption curves show a characteristic diphasic course: the quick uptake of half a mole of oxygen per mole of substrate, in aggreement with a typical oxidative deamination, is followed by a slow extra oxygen consumption. The first product of the reaction is the corresponding alpha-oxo-epsilon-amino acid, which spontaneously cyclizes to the internal Schiff base 5-6-dihydro-delta 3,1,4-thiazin-3-carboxylic acid (TZCA). This latter has been identified by its UV absorption spectrum, by some chemical reactions, by paper chromatography, and by the production of cystamine and glyoxylic acid after prolonged oxidation of thialysine followed by acid hydrolysis. The possibility of an alpha-beta elimination reaction giving rise to cysteamine from thialysine, coupled to the oxidative deamination, has been excluded
On the product of the reaction between cysteamine and 3-bromopyruvate.
No full textSome properties of TZCA, the addition compounds of cysteamine and 3-bromopyruvate, have been investigated. From the behaviour of the UV absorption spectra in acidic and alkaline solutions in the presence or absence of oxygen, it was shown that the instability of TZCA was imputable to an oxidative degradation. It was further shown that TZCA undergoes in alkali spontaneous oxidative decarboxylation, and that the arising product may be hydrolyzed to cystamine and glyoxylic acid. Some chemical reactions and the paper chromatographic behaviour of TZCA are reported. It was shown that TZCA, despite its great instability, may be the reactions described, and thus differentiated from other adducts of bromopyruvate and different aminothiols
Oxidative deamination of Se-(1-carboxyethyl)-,Se-(1-carboxypropyl)- and Se-(2-carboxyethyl)-selenocysteine by snake venom L-aminoacid oxidase.
No full textDetails are reported for the synthesis of Se-(1-carboxyethyl)-selenocysteine (1-CESeC), Se-(1-carboxypropyl)-selenocysteine (1-CPSeC) and Se-(2-carboxyethyl)-selenocysteine (2-CESeC). They can be obtained in pure cristalline form with good yield. Some chromatographic properties, useful for their identification, are described. The three aminoacids are good substrates for snake venom L-aminoacid oxidase, giving the corresponding alpha-ketoacids as reaction products
Action of thiazolidine-2-carboxylic acid, a proline analog, on protein synthesizing systems
No full text[No abstract available
Reactive oxygen species (ROS) modulation o epithelial cells expressing high-risk HPV oncogenes
No full textSynthesis and chromatographic properties of 1,3-thiazane-2-carboxylic acid (beta-homothiaproline).
No full textDetails are reported for the synthesis of 1,3-thiazane-2-carboxylic acid, or beta-homothiaproline, 3-Bromopropylamine is allowed to react with sodium thiosulfate to give S-sulfo-homocysteamine, which is then split in acidic medium to homocystamine. Homocystamine is reduced by a slight excess of dithioerythritol and allowed to react with sodium glyoxylate. beta-Homothiaproline is then isolated by ion exchange on Dowex 50 and finally obtained in pure crystalline form, with a fairly good yield. Some chemical and chromatographic properties of beta-homothiaproline, in comparison with gamma-homothiaproline (1,3-thiazane-4-carboxylic acid), beta-thiaproline (thiazolidine-2-carboxylic acid) and gamma-thiaproline (thiazolidine-4-carboxylic acid) are described
Beta-selenaproline as competitive inhibitor of proline activation.
No full textBeta-Selenaproline, a proline analog having the beta-methylene group substituted by a selenium atom, has been tested in ATP-PPi exchange reaction catalyzed by either Escherichia coli or rat liver aminoacyl-tRNA synthetases. It has been shown that with both enzymatic systems beta-selenaproline does not give rise to ATP-PPi exchange, but specifically inhibits proline activation. The inhibition is of fully competitive type and the Ki values, lower than the Km values for proline, show that beta-selenaproline binds to the synthetases with high affinity. The inability to form the complex with AMP, taking into account also the behavior of gamma-selenaproline and other proline analogs, has been ascribed to the presence of the selenium atom in the beta-position
Transport systems for lysine, thialysine and selenalysine in E. coli KL16.
No full textTwo lysine transport systems have been identified in E. coli KL16. They differ in their affinity for lysine, one showing a KM of 0.36 microM and the other a KM of 4.7 microM. Different compounds with chemical similarities to lysine were tested for their capacity to interfere with lysine transport. Among these only thialysine and selenalysine competitively inhibit lysine transport. The inhibition is on both transport systems. Thialysine shows a KI of 4 microM for the low affinity system and a KI of 8 microM for the high affinity system. Selenalysine shows values of 6 microM and 12 microM respectively
- …
