Environmental Engineering Reference
In-Depth Information
chloroplasts (Komissarov
2003
; Bach
1894
; Chance et al.
1979
; Halliwell
1981
;
Holland et al.
1982
; Wilhelm et al.
1996
,
1997
,
1999
; Halliwell and Gutteridge
1999
; López-Huertas et al.
1999
; Baker and Graham
2002
; del Río et al.
2006
;
Krieger-Liszkay et al.
2008
; Lyubimov and Zastrizhnaya
1992a
,
b
; Turrens
1997
;
Karuppanapandian et al.
2011
). H
2
O
2
is also detected in the lens of the human eye
and cataracts, aqueous humor and urine, in expired human breath and rat breath.
Furthermore, increased H
2
O
2
concentrations are also observed in patients with the
adult respiratory distress syndrome, in patients with a cardiopulmonary bypass, in
people exposed to ozone, in alveolar and peritoneal macrophages isolated from
rats exposed to hypoxia, and in the breath of smokers (Wilhelm et al.
1996
,
1997
;
Bhuyan and Bhuyan
1977
; Spector and Garner
1981
; Williams and Chance
1983
;
Ramachandran et al.
1991
; Wilson et al.
1993
; Nowak et al.
1996
; Madden et al.
1997
).
It has also been observed that oral bacteria may produce H
2
O
2
(Thomas
and Pera
1983
) and that several enzymes, including glycollate and urate oxi-
dases, can produce H
2
O
2
. It is calculated that 82 nM of H
2
O
2
is produced per
g of tissue per min in perfused livers isolated from normally fed rats (Chance
et al.
1979
). The H
2
O
2
production rate is increased with inclusion of glycollate
or urate in the perfusion medium. H
2
O
2
is a precursor of HO
•
, a strong oxi-
dizing agent, which is mostly formed either in the Fenton-type reaction in the
presence of transition metals or via the Haber-Weiss reaction in the presence of
superoxide and iron (Fong et al.
1976
). Catalase, the enzyme that metabolizes
H
2
O
2
to H
2
O and O
2
is detected in liver, kidney, blood, mucous membranes
and other highly vascularized tissues (Sohal et al.
1994
; Matutte et al.
2000
).
Correspondingly, detoxification of H
2
O
2
by catalase has also been observed in
the rabbit iris-ciliary body and in cultured lens epithelial cells (Delamere and
Williams
1985
; Giblin et al.
1990
).
The radical
O
2
•−
can rapidly produce H
2
O
2
and O
2
by the following reaction
(Eq.
3.26
) (Koppenol
1976
):
2O
2
•−
+
2H
+
→
H
2
O
2
+
O
2
k
=
4. 5
×
10
5
M
−
1
s
−
1
at pH 7 and 22
◦
C
(3.26)
although the reaction between
O
2
•−
AND HO
2
•
is much faster.
•
−
Similarly, HO
can react with O
2
to produce H
2
O and O
2
(Eq.
3.27
) (Koppenol
1976
):
HO
•
+
O
2
−
+
H
+
→
O
2
+
H
2
O
(3.27)
Several studies have proposed that
1
O
2
is formed in the cells or in PSII
(Halliwell and Gutteridge
1999
; Krieger-Liszkay et al.
2008
; Kautsky et al.
1931
;
Durrant et al.
1990
; Vass et al.
1992
; Macpherson et al.
1993
; Hideg et al.
1994
;
Keren et al.
1997
; Fufezan et al.
2002
; Krieger-Liszkay
2005
). The chlorophyll
(Chl) triplet state can produce the very reactive
1
O
2
upon reaction with ground
state
3
O
2
, if it is not efficiently quenched (Krieger-Liszkay et al.
2008
). The life-
time of
1
O
2
in a cell is estimated into approximately 3 s (Skovsen et al.
2005
; Hatz
et al.
2007
).
