One of the enzymes that handles superoxide is superoxide dismutase. Actually, this is a family of enzymes, using various metals as cofactors, which catalyze the dismutation of superoxide:
(1) M(n+1)+ − SOD + O2− → Mn+ − SOD + O2
(2) Mn+ − SOD + O2− + 2H+ → M(n+1)+ − SOD + H2O2.
where M = Cu (n=1) ; Mn (n=2) ; Fe (n=2) ; Ni (n=2).
I know, I know...your eyes just
glazed over and your brain just went offline. Bottom line:
superoxide production leads to the formation of hydrogen peroxide.
That's bad enough, because peroxide is itself a radical that is not
good for you. But through an iron-catalyzed process known as the Fenton reaction, peroxide can be converted to OH·
, the hydroxyl radical.
(1) Fe2+ + H2O2 → Fe3+ + OH·
(2) Fe3+ + H2O2 → Fe2+ + OOH·
Two molecules of hydrogen peroxide are converted into two hydroxyl radicals
and water. The generated radicals then engage in secondary reactions. More electrons running loose.