The Oxidative Metabolism of Antarctic Fish: Some Peculiar Aspects of Cold Adaptation
135
Table 2. Coenzyme Q and vitamin E content of liver mitochondria and debris of
Antarctic fish and a temperate freshwater fish
CoenzymeQ
Vitamin E
(ng/mg protein)
(ng/mg protein)
Mitochondria
Debris
Mitochondria
Debris
C. aceratus
S02 a
164 a
127
117
N. coriiceps
960 a
275 a
333
279
0. mykiss
1233 b
44S b
15
10
a = Coenzyme Q9
b = Coenzyme QlO
mechanisms was recently investigated [27]. Owing to the obvious
evolutionary importance of these particular aspects the attention has been
focused on the concentration of coenzyme Q and of vitamin E and on the
presence of copper, zinc and selenium (not shown) which display an
essential role respectively for the activity of superoxide dismutase,
glutathione peroxidase and catalase. The obtained results seem to confIrm
the above outlined hypothesis showing an overall increase of the
antioxidant defenses as reported in Tables I and 2. In fact the vitamin E
content of liver mitochondria from Antarctic fIshes is between 10 and 30
times higher than that observed in the case of trout, and COQ9 , even
though present in a slightly lower amount with respect to COQIO in the
trout, seems to show a higher antioxidant activity [29]. Furthermore, it is
worthwhile to outline that in the blood, the content of COQ9 in all the
species of the Antarctic fIshes examined is 2 to 5 times higher than that of
COQIO in trout.
The presence of the Q9 form of coenzyme Q in substitution of the QIO
form normally found in cells from temperate fIshes as well as from most
vertebrates may well be another interesting characteristic of Antarctic fIsh.
Thus, although the physiological reason for such substitution is still
matter of research it may be important to outline that the two different
forms of coenzyme Q differ in their respective crystallization temperature
which is + 0.5 °C for Q9 and + 9.7 °C for QIO. In the microenvironments, in
vivo, where crystallization of the compound cannot be excluded, this could
impair the right functioning of the respiratory chain with great troubles for
the whole organism. In this respect it is particularly suggestive that in
Antarctic fIshes QIO is substituted by Q9 whose crystallization temperature
is only slightly higher than sea water temperature. On the whole, the
presence of Q9 seems the result of an adaptive strategy by which the
135
Table 2. Coenzyme Q and vitamin E content of liver mitochondria and debris of
Antarctic fish and a temperate freshwater fish
CoenzymeQ
Vitamin E
(ng/mg protein)
(ng/mg protein)
Mitochondria
Debris
Mitochondria
Debris
C. aceratus
S02 a
164 a
127
117
N. coriiceps
960 a
275 a
333
279
0. mykiss
1233 b
44S b
15
10
a = Coenzyme Q9
b = Coenzyme QlO
mechanisms was recently investigated [27]. Owing to the obvious
evolutionary importance of these particular aspects the attention has been
focused on the concentration of coenzyme Q and of vitamin E and on the
presence of copper, zinc and selenium (not shown) which display an
essential role respectively for the activity of superoxide dismutase,
glutathione peroxidase and catalase. The obtained results seem to confIrm
the above outlined hypothesis showing an overall increase of the
antioxidant defenses as reported in Tables I and 2. In fact the vitamin E
content of liver mitochondria from Antarctic fIshes is between 10 and 30
times higher than that observed in the case of trout, and COQ9 , even
though present in a slightly lower amount with respect to COQIO in the
trout, seems to show a higher antioxidant activity [29]. Furthermore, it is
worthwhile to outline that in the blood, the content of COQ9 in all the
species of the Antarctic fIshes examined is 2 to 5 times higher than that of
COQIO in trout.
The presence of the Q9 form of coenzyme Q in substitution of the QIO
form normally found in cells from temperate fIshes as well as from most
vertebrates may well be another interesting characteristic of Antarctic fIsh.
Thus, although the physiological reason for such substitution is still
matter of research it may be important to outline that the two different
forms of coenzyme Q differ in their respective crystallization temperature
which is + 0.5 °C for Q9 and + 9.7 °C for QIO. In the microenvironments, in
vivo, where crystallization of the compound cannot be excluded, this could
impair the right functioning of the respiratory chain with great troubles for
the whole organism. In this respect it is particularly suggestive that in
Antarctic fIshes QIO is substituted by Q9 whose crystallization temperature
is only slightly higher than sea water temperature. On the whole, the
presence of Q9 seems the result of an adaptive strategy by which the