[SCAN] Oxygen and life: ways to deal with the paradox

Scan Seminar

Title:  Oxygen and life: ways to deal with the paradox

Speaker: Miguel Teixeira

From: Metalloenzymes and Molecular Bioenergetics Lab, ITQB

Abstract:

The appearance of oxygen in Earth atmosphere about 2.5 billion years ago had tremendous
impacts on life. On the first hand, it allowed the development of the most energy requiring organisms, such as multicellular life forms. But, on the other hand, it placed a continuous threat to all life forms. The controlled, enzymatic reduction of oxygen to water (by membrane-bound respiratory oxygen reductases, or soluble oxygen reductases) is harmless and associated to energy conservation and/or oxygen detoxification; among these enzymes are the flavodiiron oxygen/nitric oxide reductases. On the opposite, the un-controlled, univalent reduction processes of O2 release quite toxic species, such as the superoxide anion, hydrogen peroxide or the deadly hydroxyl radical. All living beings known to date possess enzymes to deal with both superoxide and hydrogen peroxide, accelerating their removal. Among such enzymes are the superoxide reductases. After a general over view on the chemical and biological background on these chemical and metabolic processes, our latest data on both flavodiiron reductases, namely possible determinants for their substrate specificity, and on 1-Fe superoxide reductases, namely their catalytic mechanisms and structures, will be presented.

• Gonçalves VL, Vicente JB, Pinto L, Romão CV, Frazão C, Sarti P, Giuffrè A, Teixeira M (2014), . Flavodiiron Oxygen Reductase from Entamoeba histolytica: Modulation of substrate preference by tyrosine 271 and lysine 53, J Biol Chem. 2014 Oct 10;289(41):28260-70
• Sheng Y, Abreu IA, Cabelli DE, Maroney MJ, Miller AF, Teixeira M, Valentine JS. (2014), Superoxide dismutases and superoxide reductases., Chem Rev. ,114(7), 3854-3918.