Oxidative stress is believed to play a role in the pathogenesis of several diseases, in
cludingdiabetes and inborn errors of metabolism. The types of oxidative damage observed in thesepathologies have been attributed to the ex
cessive produ
ction of rea
ctive intermediates relatingto the a
ccumulation of toxi
c metabolites. The produ
ction of extremely oxidizing peroxynitrite
can also be high in these pathologies. We study here the oxidation initiated by peroxynitriteof the ethyl esters of a
cetoa
cetate (EAA) and 2-methyla
cetoa
cetate (EMAA), metabolites thata
ccumulate in diabetes and isoleu
cinemia, respe
ctively. Oxygen
consumption studies have
confirmed that peroxynitrite promotes the aerobi
c oxidation of EAA and EMAA in phosphatebuffer. These rea
ctions were a
ccompanied by ultraweak light emission, whi
ch probably arisesfrom triplet
carbonyl produ
cts formed by thermolysis of dioxetane intermediates. The kineti
csof oxygen uptake and
chemilumines
cen
ce by EAA and EMAA was strongly affe
cted by thephosphate ion, known to
catalyze
carbonyl enolization and nu
cleophili
c additions to
carbonyls.The rea
ction pH profiles obtained by oxygen
consumption and
chemilumines
cen
ce measurements indi
cated that the peroxynitrite anion was the initiator of EAA and EMAA aerobi
coxidation. EPR spin-trapping studies with the spin traps 3,5-dibromo-4-nitrosobenzenesulfoni
ca
cid and 2-methyl-2-nitrosopropane showed the intermedia
cy of methyl and a
carbon-
centeredradi
cal (
CH
2COR) in the oxidation of EAA by peroxynitrite. In the
case of EMAA, a tertiary
carbon-
centered radi
cal (
EMAA) and an a
cyl radi
cal were dete
cted, the latter probably resultingfrom the
cleavage of a triplet
carbonyl produ
ct. Superstoi
chiometri
c formation of a
cetate fromboth substrates
confirmed the o
ccurren
ce of oxygen-dependent
chain rea
ctions, here proposedto be initiated by one-ele
ctron abstra
ction from the enoli
c form of the substrates. The freeradi
cals and ele
ctroni
cally ex
cited spe
cies generated in the oxidation of EAA and EMAA mayhelp shed further light on the mole
cular basis of these diseases.