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C Cini

Publications and source records attributed to C Cini.

51 records · Page 3Linked to original sources
PubMed1979

Action of thiazolidine-2-carboxylic acid, a proline analog, on protein synthesizing systems.

Thiazolidine-2-carboxylic acid, or beta-thiaproline, is a proline analog in which the beta methylene group of proline is substituted by a sulfur atom. It has been deomonstrated that beta-thiaproline is activated and transferred to tRNAPro by Escherichia coli and rat liver aminoacyl-tRNA synthetases, and inhibits proline incorporation into polypeptides in protein synthesizing systems from E. coli, rat liver or rabbit reticulocytes. In mammalian systems beta-thiaproline inhibits also leucine incorporation; in rabbit reticulocyte lysate it inhibits ribosome run-off. Both these effects may be explained by the fact that beta-thiaproline once incorporated into the growing polypeptide chain impairs its further elongation, as shown by experiments made with puromycin. All tests were performed in comparison with thiazolidine-4-carboxylic acid, or gamma-thiaproline, another proline analog having the gamma methylene group substituted by a sulfur atom; it was shown that in all the reactions studied both compounds act as competitive inhibitors of proline. Some differences in the effects of the two analogs have been evidenced: in almost all the reactions and mainly in the whole protein synthesizing systems, beta-thiaproline shows an higher inhibitory activity.

Amino Acids, Sulfur↗
PubMedDate not supplied

Oxidative deamination of epsilon-N-acetylthialysine and epsilon-N-acetylselenalysine by snake venom L-aminoacid oxidase.

epsilon-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.

Amino Acid Oxidoreductases↗
PubMedDate not supplied

Pyridoxal phosphate catalyzed alpha-beta elimination of selenahomolysine.

In the presence of pyridoxal phosphate selenahomolysine undergoes alpha-beta elimination with production of pyruvate, ammonia and selenohomocysteamine. If the reaction occurs in anaerobic conditions the coupling of pyridoxal phosphate with selenohomocysteamine in a tetrahydro-selenazine ring may be detected by the appearance of an absorption band at 320 nm. In the presence of air the autoxidation rate of selenohomocysteamine is too high to allow the detection of the selenazine derivative. The results obtained add to the previously reported ones indicating that selenium- and sulfur-containing aminoacids react in quite the same way in the non enzymic model studied.

Catalysis↗
PubMedDate not supplied

Studies on recognition of selenahomolysine by aminoacid transport systems and aminocyl-tRNA synthetase.

In E. coli, Se-3 aminopropylselenocysteine or selenahomolysine (SeHL) does not affect intracellular lysine transport, i.e. it cannot bind E. coli lysine transport systems. In CHO cells it inhibits cationic aminoacid transport system, but only in the presence of Na+, this indicating that it behaves like polar neutral aminoacids. On the other hand, it poorly affects leucine transport both in the presence and in the absence of Na+. SeHL is not activated by aminoacyl-tRNA synthetase preparations from bacterial and mammalian sources, thus it cannot be utilized for protein synthesis.

Amino Acids↗
PubMedDate not supplied

On the product of the reaction between cysteamine and 3-bromopyruvate.

Some 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.

Chemical Phenomena↗
PubMedDate not supplied

Oxidative deamination of thialysine by snake venom L-aminoacid oxidase.

Thialysine 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.

Amino Acid Oxidoreductases↗
PubMedDate not supplied

Oxidation of D-thiazolidine-4-carboxylic acid by hog kidney D-aminoacid oxidase.

D-Thiazolidine-4-carboxylic acid is a good substrate for hog kidney D-aminoacid oxidase. Data are presented showing that the only oxidation product is delta 3-thiazoline-4-carboxylic acid, which does not undergo further spontaneous degradation. Thus, the oxidation of D-thiazolidine-4-carboxylic acid by D-aminoacid oxidase differs considerably from the oxidation of its L-isomer catalyzed by rat liver mitochondria which gives as final product N-formylcystine, possibly through the intermediate delta 2-thiazoline-4-carboxylic acid.

Animals↗
PubMedDate not supplied

Oxidation of beta-DL-thiaproline, a possible natural substrate of D-aminoacid oxidase.

Beta-DL-Thiaproline (thiazolidine 2-carboxylic acid) is a good substrate for hog kidney D-aminoacid oxidase. Unlike other known substrates, beta-thiaproline is better oxidized at neutral than at alkaline pH. At neutral pH beta-thiaproline is a better substrate than D-proline. Beta-DL-thiaproline is fully oxidized to delta 2 thiazoline 2-carboxylic acid, which in acidic medium is hydrolyzed to N-oxalylcysteamine. These results may support the suggestion that beta-thiaproline, arising in vivo from cysteamine and glyoxylate, can be a possible physiological substrate for D-aminoacid oxidase.

Amino Acids, Sulfur↗
PubMedDate not supplied

Thialysine and selenalysine utilization for protein synthesis by E. coli in comparison with lysine.

Utilization of thialysine and selenalysine for protein synthesis by a lysine requiring E. coli mutant was studied. Incorporation into proteins of thialysine or selenalysine, added to culture medium together with lysine, becomes evident when the amount of available lysine in the medium is highly reduced, that is the mutant utilizes the isologs only after all the available natural aminoacid has been utilized. Compared to selenalysine, thialysine is better utilized; when both isologs are present in the medium at equal concentrations, up to 46% of protein lysine is substituted by thialysine and only 12% by selenalysine.

Cysteine↗
PubMedDate not supplied

Synthesis and chromatographic properties of 1,3-thiazane-2-carboxylic acid (beta-homothiaproline).

Details 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.

Amino Acids, Sulfur↗
PubMedDate not supplied

Carboxymethyl-selenopyruvic acid as the product of the oxidative deamination of carboxymethyl-selenocysteine.

CMSeC labeled with 14C in the carboxymethyl moiety was incubated with snake venom L-aminoacid oxidase. As the product of the reaction only one ketoacid was detected, which retained all the radioactivity of the oxidized substrate. This clearly shows that no breakdown of the C-Se bond of CMSeC occurs during its oxidation, and confirms previously reported data indicating that the ketoacid arising from CMSeC is CMSeP.

Amino Acid Oxidoreductases↗