575
Photosynthesis in Nature: A New Look
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 oxidases, 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 oxidizing 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):
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):
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 lifetime of 1 O 2 in a cell is estimated into approximately 3 s (Skovsen et al. 2005; Hatz
et al. 2007).
(3.26)
2O 2
•− + 2H
+ → H 2 O 2 + O 2 k = 4. 5 × 10
5 M
−1 s
−1 at pH 7 and 22
◦
C
(3.27)
HO
• + O 2
− + H
+ → O 2 + H 2 O
Photosynthesis in Nature: A New Look
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 oxidases, 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 oxidizing 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):
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):
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 lifetime of 1 O 2 in a cell is estimated into approximately 3 s (Skovsen et al. 2005; Hatz
et al. 2007).
(3.26)
2O 2
•− + 2H
+ → H 2 O 2 + O 2 k = 4. 5 × 10
5 M
−1 s
−1 at pH 7 and 22
◦
C
(3.27)
HO
• + O 2
− + H
+ → O 2 + H 2 O