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Biomedical subjects

G Federici

Publications and source records attributed to G Federici.

At least 163 records · Page 9Linked to original sources
PubMed1982

Effect of physiological reducing compounds on the inactivation of tyrosine aminotransferase from guinea-pig liver.

1. Tyrosine aminotransferase from guinea-pig liver is inactivated at neutral pH by a factor localized in the microsomal fraction. The inactivation, independent of exogenous L-cysteine, is rapidly reversed by addition of dithiothreitol. 2. The effects of physiological reducing agents on the enzyme inactivation were investigated. L-Cysteine and L-cysteamine enhance the inactivation rate of the enzyme in the presence of microsomal membranes, and also they are able to bring about the loss in enzyme activity independently of microsomal action. Reduced glutathione, at physiological concentration, and NADPH decrease the inactivation rate. Other physiological reducing compounds, as well as oxidized glutathione and NADP+, are without effect. 3. Neither reduced glutathione nor NADPH, unlike dithiothreitol and mercaptoethanol, is able to restore the activity of partially inactivated tyrosine aminotransferase. 4. It is proposed that the intracellular concentration of reduced glutathione might modulate the rate of inactivation of the enzyme in vivo.

Animals↗
PubMed1982

Glutathione S-transferase activity from guinea-pig brain: a comparison with hepatic multiple forms.

1. Specific activities of glutathione S-transferase towards four model substrates were determined in guinea-pig brain 50,000 g supernatant and compared with those obtained for liver and kidney extract. 2. By using 1-chloro-2,4-dinitrobenzene as substrate, glutathione S-transferase activity was measured in different anatomical regions of brain; cerebellum expressed the highest conjugating capacity. 3. Brain glutathione S-transferase was resolved into four major peaks (PI 6.10, 6.60, 7.15, 7.65) each having similar kinetic constants for both substrates GSH and 1-chloro-2,4-dinitrobenzene. 4. Likewise, four forms, focused at pH 6.45, 7.14, 7.50 and 8.88, were obtained from liver. 5. Unlike hepatic tissue, brain does not possess the highly alkaline form which displays Se-independent GSH peroxidase activity. 6. Several psychotropic agents, including chlorpromazine and chlorazepate, produced a considerable in vitro inhibition on brain transferase activity.

Animals↗
PubMed1982

Binding of inactivated tyrosine aminotransferase to microsomal membranes.

Tyrosine aminotransferase from guinea pig liver spontaneously inactivates both in crude homogenates and in tissue slices. In the course of inactivation the cytosolic enzyme progressively translocates only into the microsomal fraction under an inactive form. Translocated enzyme activity can be restored by dithiothreitol addition which also produces the release of the enzyme from the microsomal particles. The specific binding of tyrosine aminotransferase to microsomal particles as a critical event for subsequent proteolytic degradation of the enzyme is postulated.

Animals↗
PubMed1982

L-lanthionine oxidation by snake venom L-amino acid oxidase.

L-Lanthionine is oxidized by snake venom L-amino acid oxidase with the release of one mole of ammonia per mole of lanthionine. Spectrophotometric, chromatographic, and analytical properties are all consistent with the identification of the mono-keto derivative of lanthionine as the first enzymatic product of the reaction. This then cyclizes into a dihydrothiazine dicarboxylic acid which is further subject to spontaneous changes. Authentic samples of the thiazine derivative have been prepared by interacting L-cysteine with bromopyruvic acid. The properties of the synthetic product are described and compared with those exhibited by the enzymatic product.

Alanine↗
PubMed1981

Effect of a new pyrimidine analog on Bacillus subtilis growth.

2-Amino-5-ethoxycarbonylpyrimidine-4(3H)-one, a pyrimidine analog, inhibited growth of Bacillus subtilis. Data were obtained which suggested that the analog interfered with the methylation process. A mutant resistant to the inhibitor was isolated, and the mutation was mapped.

Bacillus subtilis↗
PubMed1979

[Spectral properties of perselenosulfide].

The riductive scission of a diselenide (selenocystamine) produced by disulfide gives the perselenosulfide, a new compound. Its formation kinetics, carried out a several pH values, were recorded spectrophotometrically at 375 nm. The lability of perselenosulfide bond by cianolysis has been demonstrated.

Selenium↗
PubMed1979

[Preliminary study of the physical chemistry and catalytic properties of glutathione-S-transferase from human placenta].

Glutathione-S-transferase activity has been identified in the cytosol of human placenta. The specific activity measured is about 50% of that found in human liver. While some kinetic data have a close correspondence with those attributed to transferases of other sources, the molecular weight (60.000 daltons) and electric properties of this protein are unusual. The inhibitory effect of several non-substrate compounds suggests that also the placental Glutathione-S-transferase may play some role in detoxication of exogenous substances.

Cephaloridine↗
PubMed1978

Enzymatic oxidation of mercaptoethanol to isethinic acid and isethionic acid.

The enzymatic oxidation of mercaptoethanol by purified cysteamine oxygenase has been studied. Products were identified by chromatography as isethinic acid (2-hydroxyethan-sulfinic acid) and isethionic acid. Other features of the reaction, as cofactor requirement, the influence of the enzyme concentration on the stage of oxidation, the biological significance of this reaction are also discussed.

Alkanesulfonates↗
PubMed1978

Oxidation of hypotaurine to taurine by ultraviolet irradiation.

Oxidation of hypotaurine to taurine is known to occur in vivo. Search for an enzyme performing that oxidation has been unsuccessful. However, fast and quantitative oxidation of hypotaurine (and other sulfinates) by ultraviolet irradiation has now been observed. The reaction is first order and pH-dependent, and its rate depends strongly on the kind of sulfinate irradiated. Only the corresponding sulfonate is recovered as the product under the relatively mild conditions used. Catalase or superoxide dismutase does not affect the oxidation, which is oxygen-dependent. A simple reaction scheme is proposed to account for the findings.

Cysteine↗