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Reduced enzymatic antioxidative defense in deep-sea fish
B J Janssens1, J J Childress, F Baguet
1Animal Biology Unit, Université Catholique de Louvain, Croix du Sud, B-1348 Louvain-la-Neuve, Belgium. Janssens@bani.ucl.ac.be
The Journal of Experimental Biology
|November 15, 2000
Summary
Deep-sea fish possess reduced antioxidant enzyme activity, with superoxide dismutase (SOD) and glutathione peroxidase (GPX) levels decreasing with depth. Catalase (CAT) activity remained constant, suggesting varied roles in oxidative stress defense.
Area of Science:
- Marine biology
- Biochemistry
- Oceanography
Background:
- Oxygen is vital for aerobic life but produces toxic reactive oxygen species (ROS) causing oxidative stress.
- Meso- and bathypelagic ocean zones, with low oxygen and metabolic rates, may offer refuge from ROS.
- Antioxidative enzymes like superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) combat ROS.
Purpose of the Study:
- Investigate antioxidative enzyme activities in deep-sea fish.
- Determine if deep-sea environments reduce the need for antioxidant defenses.
- Explore the relationship between metabolic rate, depth, and enzyme activity.
Main Methods:
- Analyzed SOD, CAT, and GPX activities in 16 deep-sea fish species (0-1300m).
- Measured citrate synthase activity as an indicator of metabolic rate.
- Compared enzyme activities across different tissues and depths.
Main Results:
- All tissues and species showed detectable enzyme activities.
- SOD and GPX activities decreased with depth, correlating with reduced metabolic rate.
- CAT activity was unaffected by depth or metabolic rate.
- Bioluminescent organs exhibited high enzyme levels.
Conclusions:
- SOD and GPX likely defend against metabolically produced ROS, adjusting to lower deep-sea metabolism.
- Constant CAT activity suggests a role beyond metabolic ROS defense, possibly related to other stressors.
- Deep-sea fish may have a reduced, but specifically adapted, antioxidant defense system.