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L Landi

Publications and source records attributed to L Landi.

At least 73 records · Page 4Linked to original sources
PubMed1981

Effect of ubiquinone extraction on ubiquinol-1 oxidase activity in beef heart mitochondria.

Extraction of endogenous ubiquinone with different methods does not influence ubiquinol oxidase activity in lyophilized mitochondria in terms of KM, although a decrease of Vmax is sometimes observed. Experiments with submitochondrial particles from a UQ-deficient mutant of S. cerevisiae confirm the results with UQ-depleted mitochondria and support the idea that endogenous ubiquinone is not required for the oxidation of exogenous ubiquinols by complex III.

Animals↗
PubMed1979

Effect of endogenous ubiquinone on the reduction and oxidation of short exogenous ubiquinone homologs in beef heart mitochondria.

The enzymic activities NADH-ubiquinone reductase, succinate-ubiquinone reductase and ubiquinol oxidase were evaluated in beef heart mitochondria in presence of short ubiquinone homologs. Preliminar data obtained indicate that short chain homologs, less lipophilic than natural ubiquinone do not reach the reoxidation site in absence of endogenous ubiquinone.

Animals↗
PubMed1979

Lipid protein interactions in mitochondria. VII. A comparison of the effects of lipid removal and lipid perturbation of the kinetic properties of mitochondrial ATPase.

We investigated the kinetics of mitochondrial ATPase in bovine heart mitochondria and submitochondrial particles upon treatment with phospholipase A2, or upon addition of n-butanol to perturb the lipid protein interactions. The changes observed are the following: (1) Lipid removal or perturbation with butanol is accompanied by loss of ATPase activity with decrease of both V and of the KM for ATP. (2) There are changes of activation energy of ATPase activity at temperatures above the discontinuity normally observed for membrane-bound enzymes in mitochondria. In particular, butanol abolishes the discontinuity, and induces a constant activation energy of about 32 kcal/mol in the range 8--37 degrees C. (3) Butanol modifies the pH dependence of ATPase shifting the pH optimum from around 10 to less alkaline values. The optimum for Mg2+ concentrations is increased by the solvent. (4) Treatment with phospholipase A2 results in a removal of oligomycin-sensitive ATPase, whereas butanol addition prevents oligomycin inhibition of ATPase. (5) In beef heart mitochondria, a spin-labelled analog of the inhibitor, dicyclohexyl carbodiimide, did not show any change in environment upon butanol addition, unlike that found in mitochondria from Saccharomyces cerevisiae.

Adenosine Triphosphatases↗
PubMed1970

Effects of thyroxine on the synthesis of folate coenzymes in rat liver.

1. The effects of thyroidectomy and of ;acute' and ;chronic' administration of thyroxine on the synthesis of folate coenzymes were studied by determining the liver contents of folate active derivatives and the enzymic activities involved in their biosynthesis. The effect of thyroxine on the same enzymes in vitro was also studied. 2. In thyroidectomized rats the liver contents of folate coenzymes did not change except for a slight decrease in the contents of 5-formyltetrahydrofolate and tetrahydrofolate compared with those in control rats. 3. In the same animals serine hydroxymethyltransferase and formyltetrahydrofolate synthetase activities decreased markedly. 4. The ;chronic' administration of thyroxine to thyroidectomized rats caused more evident variations in the liver contents of folate coenzymes and in particular a decrease in the contents of 5-formyltetrahydrofolate, tetrahydrofolate, 5(or 10)-formyl derivatives of tetrahydropteroylpolyglutamate and of 5(or 10)-formyl derivatives of pteroylpolyglutamate. 5. The enzymic activities did not show significant variations. 6. The ;acute' administration of thyroxine caused changes in the liver contents of some folate derivatives such as 10-formyldihydrofolate, 10-formylfolate, tetrahydrofolate and the 10-formyl derivative of dihydropteroylpolyglutamate. In these animals also the enzymic activities were unchanged. 7. No effect of thyroxine on enzymic activities in vitro was observed.

Animals↗