Biomedical subjects

I Fabregat

Publications and source records attributed to I Fabregat.

41 records · Page 3Linked to original sources

PubMed1987

The NADPH-producing pathways (pentose phosphate and malic enzyme) are regulated by the NADPH consumption in rat mammary gland.

We have studied the changes in the activity of the pentose phosphate cycle and the malic enzyme produced by the activation or inhibition of different NADPH-consuming pathways. Kynurenate, an acetyl-CoA-carboxylase inhibitor produced a decrease in the flux through the NADPH-producing pathways pentose phosphate cycle and malic enzyme. Acini (isolated from mammary gland) incubated in the presence of ter-butyl-hydroperoxide, a compound which is metabolized via a NADPH-consuming pathway, showed a substantial increase in the pentose phosphate cycle and the malic enzyme pathways.

Animals↗

PubMed1985

The pentose phosphate cycle is regulated by NADPH/NADP ratio in rat liver.

The changes in the activity of the pentose phosphate cycle produced by the activation or inhibition of different NADPH-consuming pathways have been studied. The inhibition of fatty acid synthesis by kynurenate produced to the same extent, inhibition of the pentose phosphate cycle activity and an increase (about twofold) in the NADPH/NADP ratio. The addition of ter-butyl-hydroperoxide or paraquat, which is metabolized via NADPH-consuming pathways, produced the activation of the pentose phosphate cycle and a decrease in the NADPH/NADP ratio (about threefold). The plot of the NADPH/NADP ratio versus the pentose phosphate cycle activity gave a straight line with a regression index of 0.999. The regulation of the pentose phosphate cycle mainly by the intracellular NADPH/NADP ratio is discussed.

Animals↗

PubMed1984

Interaction with protein SH groups could be involved in adriamycin cardiotoxicity.

The use of the antineoplastic agent adriamycin is limited by its cardiotoxicity. The mechanism of cardiotoxicity has been investigated through the study of adriamycin effects on a number of heart enzymes. Adriamycin inhibited the activity of NADP-isocitrate dehydrogenase, malic enzyme, and 6-phosphogluconate dehydrogenase, three enzymes that have in common the presence of reactive SH groups involved in activity. Adriamycin action was prevented by the presence of proteins or dithioerythrol and mimicked by dithiobis dinitrobenzoate. It is suggested that adriamycin effects are due to interaction with enzyme SH groups by a product of adriamycin metabolism.

Animals↗

PubMed1983

Citrate synthase of Tetrahymena pyriformis: evolutionary and regulatory aspects.

Citrate synthase (EC 4.1.3.7) from Tetrahymena pyriformis has been purified 185-fold. The molecular weight of the native enzyme was determined to be 120,000. The enzyme is labile at low ionic strength, but can be stabilized by KCl and glycerol. It is activated by KCl at low (below 60 mM) or high concentrations, and inhibited by divalent cations (Mn2+, Mg2+, Ca2+). The Michaelis constants are 0.1 mM for oxalacetate and 0.01 mM for acetyl-CoA. The kinetics with oxalacetate exhibit negative cooperativity, with a nH = 0.66. Among the metabolites tested, only ATP and GTP can inhibit the enzyme but Mg2+ relieves the ATP inhibition. Incubation with sulfhydryl reagents (DTNB) in the absence of its substrates results in a rapid inactivation of the enzyme. It is concluded that Tetrahymena citrate synthase is closer to the enzyme from Gram-positive bacteria than to those of eucaryotes.

Adenosine Triphosphate↗

PubMed1982

[Study of the inhibition produced by adriamycin against specific enzymes in the rat heart].

Adriamycin is used for the treatment of leukemia and other neoplastic processes. Unfortunately the drug has a toxic effect on some tissues. Cardiotoxicity in particular limits the use of the drug. Several hypotheses have been given to explain adriamycin heart toxicity. The authors have studied the effect of the drug on the enzymes isocitrate dehydrogenase-NADP, malic enzyme, 6-P-gluconate dehydrogenase, malic dehydrogenase-NAD+, hexokinase, and phosphofructokinase. They observed that adriamycin inhibits the NADP-dependent enzymes, and that the sulfhydryl group of the enzymes may be involved in the inhibitory action of adriamycin.

Animals↗