Temperature dependence of superoxide dismutase activity in plankton

The effect of temperature (from 1 to 37 °C) on in vitro effective superoxide dismutase (SOD) activity of several organisms was investigated and compared. Antarctic plankton, cultures of the alga Nannochloropsis sp., and the cyanobacterium Synechococcus strain WH 7803, and pure bovine erythrocyte SOD was studied. It was found that in all cases SOD activity increased with decreasing temperature within the temperature range assayed, in the Polar as well as the temperate plankton cells. This behavior of SOD is counterintuitive in terms of our experience when looking at enzyme activity or any other chemical reaction. We suggest a theoretical explanation for this apparently odd behavior. The advantage of such behavior is that the same amount of antioxidant will act better under low temperatures when reactive oxygen species (ROS) increase. Moreover, this protective process would act in vivo at a faster pace than the ex novo enzyme synthesis.