Ti-UNic Biotech

The wonder of Superoxide Dismutase is its ability to seize and to provide free radical electrons. The so-called Disproportionation Reaction can effectively remove free radicals out of organisms.

And blue-green algae – the very first organism that initiated photosynthesis – brought the Great Oxygenation Event to earth 2.5 billion years ago. It converted the O₂ in atmosphere from originally 1% or less to 20%, which opened the prologue of biological evolution. During respiration, living organisms turn partial oxygen (O₂) into Reactive Oxygen Species (ROS), and further produces various types of free radicals. In order to resist against the harms caused by free radicals, blue-green algae evolved to generate Superoxide Dismutases (SODs).

Fig. 1  The Protein Structure of SOD inside Blue-Green Algae

In 1969, Fridovich and McCord discovered that SOD widely exists in various types of animals, plants, and microorganisms. It is a very important antioxidant inside organisms as it prevents cells from damages or mutation caused by ROS.

Fig. 2  SOD Species Diagram

When the concentration of superoxide ions inside organisms increases, Superoxide Dismutase will perform disproportionation reaction and convert superoxide ions into O2 and H2O2 (when pH = 7, the reaction speed is approximately 105 M⁻¹s⁻¹).

The SOD-catalyzed superoxide disproportionation reaction can be divided into two steps:

• Oxidation Reaction: M⁽ⁿ⁺¹⁾-SOD + O₂⁻ → Mⁿ⁺-SOD + O₂
• Redox Reaction: Mⁿ⁺-SOD + O₂⁻ + 2H⁺ → M⁽ⁿ⁺¹⁾-SOD + H₂O₂

The “M” can be metal ions such as Cu(n=1), Mn(n=2), Fe(n=2), Ni(n=2), hence SOD includes 4 activity centers such as copper/zinc, manganese, iron, or nickel. During such reactions, the oxidation state of metals performs oxidation reaction and redox reaction within n and n+1, in order to remove ROS effectively.

Fig. 3 Comparison of the ribbon structures that characterize the three families of SOD.