Superoxide dismutase (SOD) is an enzyme that defends against superoxide radical, which can initiate oxidizing chain reactions and generate other reactive oxidizing species (ROS). Iron- and manganese-superoxide dismutase (FeSOD and MnSOD) have similar amino acid sequences, structures and active site geometries. However, they perform differently. For example, FeSOD, from various sources is inactivated by hydrogen peroxide, whereas MnSOD is generally resistant [1]. Even though MnSOD is the major antioxidant enzyme in human mitochondria, the substitution of Mn by Fe will occur when mitochondrial iron homeostasis is disrupted [2]. As a result, iron is accumulated in a reactive form and competes with manganese for incorporation in SOD.  This in vivo mismetallation may relate to cancer since previous studies [3] found that many human cancer cells have altered MnSOD expression and activity. It has been proposed that Fe-substituted MnSOD (Fe(Mn)SOD ) possesses a toxic gain of function, reacting with peroxide to produce reactive radicals [4]. Therefore, our study on the reaction between H2O2 and Fe(Mn)SOD from Escherichia coli will identify products and intermediates to help us to understand the potential significance of Fe(Mn)SOD to the course and treatment of cancer.

Effect of hydrogen peroxide on the iron-substituted manganese superoxide dismutase

246th National Meeting (2013)

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