Superoxide Dismutases(SOD) are a well-established family of enzymatic metalloproteins, functioning primarily to catalyse the disproportionation of superoxide that results from cellular respiration. Biophysical and biochemical characterisation of Cu,Zn SOD have shown that the protein’s structure and enzymatic activity are dependent on proper metalation of the enzyme. SOD1 requires copper for catalytic function. Zinc is required to maintain the structure of the enzyme and promotes the formation of the dimeric form of the enzyme. Mis-metallation of SOD have been implicated as a primary cause of amyotrophic lateral sclerosis.

We noticed during the purification of SOD from bovine liver that SOD was found not only to contain copper and zinc, it had also incorporated tungsten. Tungsten(W), a non-essential trace element, is considerably understudied and often overlooked. Little has been uncovered regarding its biological relevance apart from limited literature detailing potential toxicity. The presence of W in the bovine liver SOD is likely due to trace environmental exposure. To further investigate the role of W incorporation in the toxicity of W we investigated W incorporation in SOD from mouse exposed to high levels of tungsten. We used metalloproteomics to understand the protein targets that incorporate tungsten during exposure. We characterised and tungsten-SOD1 complexes using liquid chromatography(LC) coupled to inductively coupled plasma mass spectrometry(ICP-MS).

            As expected, tungsten treated mice were observed to have significantly increased levels of tungsten-containing proteins when compared to control mice. To further understand the consequence of tungsten incorporation into SOD an fi it is bound to the Cu or Zn site we produce apo-SOD and attempted to titrate tungsten into apo-SOD. This was unscuseessful under the conditions used and suggests that a molecular cofactor maybe necessary for tungsten incorporation. Our results have implications for acute tungsten toxicity and environmental exposure due to occupational exposure working with tungsten.