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Biomedical subjects

C De Marco

Publications and source records attributed to C De Marco.

At least 55 records · Page 3Linked to original sources
PubMed1982

Thialysine utilization by E. coli and its effects on cell growth.

Thialysine can be utilized for growth by a wild type K12 strain of E. coli. It is incorporated into proteins in substitution and in competition with lysine; up to 17% of protein lysine can be substituted by thialysine. Nevertheless the presence of thialysine in the culture medium gives rise to an inhibition of cell growth rate. This effect has been correlated to the inhibition of protein synthesis rate by thialysine and to the extent of protein lysine substitution by the analog. On the other hand this substitution does not affect cell viability.

Bacterial Proteins↗
PubMed1982

Selenalysine utilization for growth and protein synthesis by a lysine requiring E. coli mutant.

Selenalysine can be utilized in substitution of lysine by a lysine requiring E. coli mutant. The presence of some lysine in the culture medium is necessary to allow selenalysine utilization for growth; in the presence of an excess of lysine, selenalysine is not utilized. When utilized, selenalysine gives rise to an increase of final growth. However, it shows some toxic effects as demonstrated by the decrease of both growth rate and cell viability. Selenalysine is incorporated into proteins in substitution of lysine. Up to a maximum of 50% of total protein lysine can be substituted. The decrease of cell viability is correlated with the extent of lysine substitution.

Cell Division↗
PubMed1981

In vivo incorporation of selenalysine in Escherichia coli proteins and its effects on cell growth.

The presence of selenalysine in the culture medium at concentration ranging from 0.05 to 0.3 mM inhibits Escherichia coli growth rate and cell viability. The inhibition of cell growth rate can be imputed to the inhibition of protein synthesis and can be only partially reverted by lysine. Selenalysine is incorporated into cellular proteins in substitution of and in competition with lysine, reaching the value of about 1% as molar fraction with respect to the total amino acids, and substituting up to 14% of protein lysine. The effect of selenalysine on cell viability can be correlated to the extent of its incorporation into proteins, and can be completely reverted by lysine. However, substitution up to 5% of protein lysine by selenalysine does not affect the viability, thus indicating that some degree of substitution can be well tolerated by the cell.

Bacterial Proteins↗
PubMed1981

Oxidation of meso-diaminosuccinic acid, a possible natural substrate for D-aspartate oxidase.

meso-Diaminosuccinic acid, a natural antagonist of aspartic acid, is a good substrate for beef kidney D-aspartate oxidase. The oxygen consumption and the ammonia production are in good agreement with the stoichiometry of a typical oxidative deamination. The deamination involves only one of the two amino groups of diaminosuccinate, and is followed by decarboxylation of the first reaction product, 2-amino-3-oxosuccinic acid. By condensation of the compounds thus originating from this latter, pyrazine 2,5-dicarboxylic acid and pyrazine 2,6-dicarboxylic acid are formed. DL-Diaminosuccinic acid is not oxidized by D-aspartate oxidase, nor does it inhibit the enzyme activity.

Amino Acid Oxidoreductases↗
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↗
PubMed1979

Thiaisoleucine and protein synthesis.

Thiaisoleucine is an isoleucine analogue having the gamma-methylene group of the valerianic carbon chain substituted by a sulphur atom. It has been demonstrated that thiaisoleucine is activated and transferred to tRNAIle by rat liver aminoacyl-tRNA synthetase and inhibits isoleucine incorporation into polypeptides in protein synthesizing systems from rat liver or rabbit reticulocytes, whereas it does not affect either leucine incorporation or ribosome run-off or polypeptide chain elongation rate. All tests were performed in comparison with O-methyl-threonine, an isoleucine analogue with the gamma-methylene group substituted by an oxygen atom. In all the reactions studied, both thiaisoleucine and O-methyl-threonine act as competitive inhibitors of isoleucine. With respect to O-methyl-threonine, thiaisoleucine shows higher activity as an isoleucine inhibitor.

Adenosine Triphosphate↗
PubMed1978

Oxidative deamination of carboxyethyl-cysteine and carboxymethyl-homocysteine.

Snake venom L-aminoacid oxidase, while inactive on 4C and 5C dicarboxylic alpha-amino acids, may oxidize their 6C and 7C homologues alpha-aminoadipic and alpha-aminopimelic acid. It has been demonstrated that the enzyme also oxidizes S-carboxyethyl-L-cysteine and S-carboxymethyl-L-homocysteine, two analogues of alpha-aminopimelic acid with the gamma or delta methylene groups substituted by a sulfur atom. As oxidation products the corresponding ketoacids were obtained. Thus substrate specificity of L-aminoacid oxidase for dicarboxylic alpha-aminoacids seems highly dependent on the carbon chain length, whereas substitution of a methylene group by a sulfur atom seems to have almost no effect. On the other hand, D-aspartate oxidase from beef kidney (active on 4C to 6C dicarboxylic alpha-aminoacids) cannot oxidize the 7C alpha-aminopimelic acid but is active on the S-carboxyethyl-D-cysteine analogue. The other aminopimelic analogue, S-carboxymethyl-D-homocysteine, is a very poor substrate. Thus the substrate specificity of D-aspartate oxidase, highly dependent on chain length, is also influenced by chain conformation. Furthermore, oxidation of either compound under study, L-aminoacid oxidase and D-aspartate oxidase, leaves unaffected the thioether bond.

Amino Acid Oxidoreductases↗
PubMed1976

Chromatographic separation of selenohypotaurine, selenotaurine, selenohomohypotaurine and selenohomotaurine.

By either paper or ion-exchange chromatography the two seleninic compounds selenohypotaurine and selenohomohypotaurine, and the two selenonic compounds selenotaurine and selenohomotaurine may be all separated from each other. On paper chromatography seleninic derivatives may be separated from the corresponding sulphinic compounds, while selenonic compounds show RF values similar to those of the corresponding sulphonic derivatives. These two latter types of compounds may be differentiated, however, since selenonic compounds liberate iodine from HI, while sulphonic compounds do not. Also by automated ion-exchange chromatography seleninic derivatives are well separated from the analogous sulphinic compounds, while selenonic compounds are eluted together with the corresponding sulphonic compounds.

Chromatography, Ion Exchange↗
PubMed1976

Selenalysine and protein synthesis.

Selenalysine is a lysine analog having the gamma-methylene group substituted by a selenium atom. It has been demonstrated that selenalysine is activated and transferred to tRNAlys by either Escherichia coli or rat liver aminoacyl-tRNA synthetases, and inhibits lysine incorporation into polypeptides in protein-synthesizing systems from E. coli, rat liver or rabbit reticulocytes. All tests were performed in comparison with thialysine, a lysine analog having the gamma-methylene group substituted by a sulfur atom. In all the reactions studied, both thialysine and selenalysine act as competitive inhibitors of lysine. With respect to thialysine, selenalysine act as competitive inhibitors of lysine. With respect to thialysine, selenalysine shows a slightly lower activity as lysine inhibitor.

Adenosine Triphosphate↗
PubMed1976

Oxidation of S-e-carboxymethyl-selenocysteine by L-aminoacid oxidase and by D-aspartate oxidase.

Se-Carboxymethyl-DL-selnocysteine (CMSeC) has been prepared in a pure crystalline form from selenocysteine and monochloracetic acid. It has been shown that CMSeC is a substrate for the L-aminoacid oxidase form snake venom and for the D-aspartate oxidase from beef kidney. Oxygen consumption and ammonia production indicate that only the L or the D form of CMSeC ar acted upon respectively by one or the other of the above enzymes. No noticeable differences were shown in the oxidation rate of CMSeC and S-carboxymethylcysteine, an indication that the substitution of a selenium for a sulfur atom in the molecule does not greatly affect the substrate specificity of the two enzymes. Data have been obtained suggesting that the product of the oxidative deamination of CMSeC Is Se-carboxymethyl-selenopyruvic acid.

Amino Acid Oxidoreductases↗