Open Access
ARTICLE
Superoxide and hydrogen peroxide productions by NO-inhibited complex III
Darío E. IGLESIAS*, Silvina S. BOMBICINO, Alberto BOVERIS, Laura B. VALDEZ
* Address correspondence to: Darío E. Iglesias, diglesias@ffyb.uba.ar
BIOCELL 2016, 40(1), 27-30. https://doi.org/10.32604/biocell.2016.40.027
Abstract
Complex III plays a central role in the mitochondrial respiratory chain transferring electrons from
ubiquinol to cytochrome c and pumping protons to the intermembrane space, contributing to the protonmotive
force. Furthermore, complex III can act as a source of O
2
•- in the presence of ubiquinol and antimycin, an
expermiental condition in which the oxidation of the cytochrome b hemes is blocked. The O
2
•- dismutation
catalyzed by superoxide dismutase produces H
2O
2, a known second messenger in redox signalling. Results from
our laboratory have shown that NO, released from GSNO or from SPER -NO or generated by mtNOS, inhibits
electron transfer at ubiquinone-cytochrome b area producing antimycin-like effects. Thus, both antimycin- and
NO-inhibited complex III showed a high content of cytochromes b in the reduced state (79 and 71%, respectively)
and an enhancement in the ubisemiquinone EPR signal at g=1.99 (42 and 35%, respectively). As consequence,
O
2
•- and H
2O
2 productions were increased, being the O
2
•-/H
2O
2 ratio equal to 1.98 in accordance with the
stoichiometry of the O
2
•- disproportionation. The interruption of the oxidation of cytochromes
b by NO leads to
an enhancement of the steady-state concentration of UQH•
, allowing cytochrome
bc1 complex to act as a source
of reactive oxygen species in physiological conditions.
Keywords
Cite This Article
IGLESIAS, D. E., BOMBICINO, S. S., BOVERIS, A., VALDEZ, L. B. (2016). Superoxide and hydrogen peroxide productions by NO-inhibited complex III.
BIOCELL, 40(1), 27–30.