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PubMed2006

In vitro interaction between homocysteine and copper ions: Potential redox implications.

Homocysteine (Hcys) has been implicated in various oxidative stress-related disorders. The presence of a thiol on its structure allows Hcys to exert a double-edge redox action. Depending on whether Cu2+ ions occur concomitantly, Hcys can either promote or prevent free radical generation and its consequences. We have addressed in vitro the interaction between Hcys and Cu2+ ions, in terms of the consequences that such interaction may have on the free radical scavenging properties of Hcys and on the redox state and redox activity of the metal. To this end, we investigated the free radical-scavenging, O2(*-)-generating, and ascorbate-oxidizing properties of the interacting species by assessing the bleaching of ABTS*+ radicals, the reduction of O2(*-)-dependent cytochrome c, and the copper-dependent oxidation of ascorbate, respectively. In addition, electron paramagnetic resonance and Cu(I)-bathocuproine formation were applied to assess the formation of paramagnetic complexes and the metal redox state. Upon a brief incubation, the Hcys/Cu2+ interaction led to a decrease in the free radical-scavenging properties of Hcys, and to a comparable loss of the thiol density. Both effects were partial and were not modified by increasing the incubation time, despite the presence of Cu2+ excess. Depending on the molar Hcys:Cu2+ ratio, the interaction resulted in the formation of mixtures that appear to contain time-stable and ascorbate-reducible Cu(II) complexes (for ratios up to 2:1), and ascorbate- and oxygen-redox-inactive Cu(I) complexes (for ratios up to 4:1). Increasing the interaction ratio beyond 4:1 was associated with the sudden appearance of an O2(*-)-generating activity. The data indicate that depending on the molar ratio of interaction, Hcys and Cu2+ react to form copper complexes that can promote either antioxidant or pro-oxidant actions. We speculate that the redox activity arising from a large molar Hcys excess may partially underlie the association between hyper-homocysteinemia and a greater risk of developing oxidative-related cardiovascular diseases.

Copper↗
PubMed1987

Influences of cellular components and redox potential of liquid concentrated culture of Lactobacillus bulgaricus on acid-producing activity and viability.

Acid-producing activity and viability of the liquid concentrated culture of Lactobacillus bulgaricus 1067 were markedly improved only when the cells were grown in a medium supplemented with Span 80 and then stored with .1% sodium ascorbate after addition of bubbling N2 into the culture. Oleic acid content of the cells increased from 17 to 38% to 39 to 54%, and the endothermic transition of the cell lipids shifted to a lower temperature when growth medium was supplemented with Span 80. During storage, the cells grown in the medium supplemented with Span 80 consumed a larger amount of lactose than those grown without Span 80. Also, the former cells had more ATP than the latter after storage at 5 degrees C for 14 d. Permeability of the cells for lactose might be improved by increased oleic acid content of the cellular components in which care the lactose incorporated into the cells would be utilized as the energy source during storage.

Animals↗
PubMed1990

Calculation of the cytochrome P-450 redox potential from kinetic data by the Marcus treatment; feasible or not?

Using calculations based on the Marcus theory (or linear approximations thereof) and existing rate constant/oxidation potential data, an attempt has been made to estimate the effective standard potential and reorganization energy of the P-450/(P-450)-.couple. Due to the limited data basis, the results only qualitatively indicate that P-450 either must possess an extremely high Eo'Fe(V)/Fe(IV) value (greater than 2.5 V!) or not act as an electron transfer oxidant at all. By similar calculations, it was found that model alkene epoxidation reactions do not follow an ET mechanism.

Cytochrome P-450 Enzyme System↗