TY  - EJOU
AU  - IGLESIAS, Darío E. 
AU  - BOMBICINO, Silvina S. 
AU  - BOVERIS, Alberto 
AU  - VALDEZ, Laura B. 

TI  - Superoxide and hydrogen peroxide productions by NO-inhibited complex III
T2  - BIOCELL

PY  - 2016
VL  - 40
IS  - 1
SN  - 1667-5746

AB  -  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<sub>2</sub>
•- in the presence of ubiquinol and antimycin, an
expermiental condition in which the oxidation of the cytochrome b hemes is blocked. The O<sub>2</sub>
•- dismutation
catalyzed by superoxide dismutase produces H<sub>2</sub>O<sub>2</sub>, 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<sub>2</sub>
•-  and H<sub>2</sub>O<sub>2</sub> productions were increased, being the O<sub>2</sub>
•-/H<sub>2</sub>O<sub>2</sub> ratio equal to 1.98 in accordance with the
stoichiometry of the O<sub>2</sub>
•- disproportionation. The interruption of the oxidation of cytochromes <i>b</i> by NO leads to
an enhancement of the steady-state concentration of UQH•
, allowing cytochrome <i>bc<sub>1</sub></i> complex to act as a source
of reactive oxygen species in physiological conditions.
KW  - S-nitrosoglutathione (GSNO)
KW  -  spermine-NONOate (SPER -NO)
KW  -  electron paramagnetic resonance (EPR)
KW  -  ubisemiquinone

DO  - 10.32604/biocell.2016.40.027