Oxygen uptake by Euglena gracilis mitochondria and chloroplasts, stimulated by ultraviolet irradiation

A possible role of the Na(+)/K(+)-ATPase for O(2) production from H(2)O(2)

We are attempting to supply a new insight on interaction between Na(+)/K(+)-ATPase and H(2)O(2). We demonstrate that in vitro the Na(+)/K(+)-ATPase, a non heme-protein, is able to disproportionate H(2)O(2) catalatically into dioxygen and water, as well as C(40) catalase. By polarography, we quantify O(2) production and by Raman spectroscopy H(2)O(2) consumption. A comparative analysis of kinetics parameters relative to O(2) production shows that for Na(+)/K(+)-ATPase the affinity of the catalytic site able to transform H(2)O(2) into O(2) is twice weaker than that for C(40) catalase. It also shows that the molar activity for O(2) production is 300-fold weaker for ATPase than for catalase. Inhibitors, pH and GSH studies highlight the differences between the heme- and nonheme-proteins. Indeed, for C(40), NaN(3) is strongly inhibiting, but much less for ATPase. The pH range for the catalatic activity of ATPase is wide (6.5 to 8.5), while it is not for C(40) catalase (optimum at pH 8). The Na(+)/K(+)-ATPase catalatic activity is reduced in presence of glutathione, while it is not the case with C(40) catalase.

Copper-adenine catalyst for O(2) production from H(2)O(2)

In solutions of CuCl2 and adenine copper can be bound to adenine. Two Cu(adenine)(2) complexes [Cu(C(5)H(5)N(5))(2)]2+/Cu(C(5)H(4)N(5))(2)] are in equilibrium with free adenine. Copper-adenine complexes present a catalytic activity (e.g., H(2)O(2) disproportionation into O(2) and water) but depending on complex concentration H(2)O(2) also strongly oxidizes the adenine within the complexes. Raman spectroscopy quantifies copper-adenine complex formation and H(2)O(2) consumption; polarography quantifies O(2) production. As for C(40) catalase, optimal catalytic capacities depend on physiological conditions, such as pH and temperature. The comparative analysis of kinetic parameters shows that the affinity for H(2)O(2) of Cu(adenine)(2) is 37-fold lower than that of C(40) catalase and that the molar activity for O(2) production is 200-fold weaker for Cu(adenine)(2) than for the enzyme. In the 10(-6)-10(-3) M range, the strong decrease of activity with raising complex concentration is explained by aggregation or stacking, which protects Cu(adenine)(2) entities from H(2)O(2) oxidation, but also decreases O(2) production.

Metabolic studies on eel (Anguilla anguilla L.) hepatocytes in primary culture: effect of 17 beta-estradiol and growth hormone

Previous studies demonstrated that native and recombinant growth hormone from mammalian and fish species potentiate the estrogenic induction of vitellogenin synthesis by cultured eel hepatocytes. In the present study, the metabolic competence (respiratory activity and estradiol catabolism) of cultured hepatocytes and their functional capacity to synthesize a specific protein, vitellogenin, in the presence of estradiol and/or bovine growth hormone was investigated. In addition, we examined the possible role of insulin-like growth factors as mediators of growth hormone. Hepatocytes retain a high level of metabolic activity under the primary culture conditions applied. Estradiol has a half life of several hours in the hepatocyte culture, and is metabolized into conjugated forms. Estradiol and/or growth hormone had no effects on respiratory activity of the cultured hepatocytes. Moreover, the estradiol catabolic parameters were not affected by growth hormone. Finally, human and trout recombinant insulin-like growth factors do not potentiate vitellogenin synthesis induced by estradiol.

Catalase activity in human spermatozoa and seminal plasma

Catalase activity was determined in human semen by measuring the oxygen burst with a Clark electrode, after H2O2 addition. Significant catalase activities (mean +/- SD) were found in migrated, motile spermatozoa (44 +/- 17 nmoles O2/min/10(8) cells) and in seminal plasma of normozoospermic men (129 +/- 59 nmoles O2/min/ml). It has been demonstrated that seminal catalase originated from prostate; however, its activity was not correlated with the usual prostatic markers (such as citric acid and zinc). Our data suggest a multiglandular function secreted by this organ. The catalase activities measured in seminal samples from asthenozoospermic, infertile men were found lower than those from normozoospermic subjects. The understanding of the relative contribution of the different enzyme systems against O2 toxicity (superoxide dismutase, catalase, glutathione peroxidase) seem to be a priority area of research to understand disturbances of sperm function.