Deciphering the effect of salts on Bilirubin Oxidases activity

Abstract

Bilirubin Oxidases (BODs) and laccases belong to the Blue Multicopper Oxidases family (MCOs). Both enzymes couple the oxidation of substrates to the reduction of O2 to H2O. In contrast to laccases, BODs display high activity and stability at neutral pH and are more tolerant to chloride [1]. These unique features make BODs useful in a large number of biotechnological applications such as biosensors for jaundice detection, dyes degradation, and as a cathodic enzyme in enzymatic biofuel cells [2]. Glucose/oxygen enzymatic biofuel cells use the energy of redox reactions catalyzed by enzymes to produce electrical energy. Glucose oxidizing enzymes such as Glucose Oxidase (GOX) and oxygen reducing enzymes such as BODs are used at the anode and at the cathode respectively. Such biofuel cells are good candidates to be implanted in the human body of diabetic people and would be the only in vivo power source able to power glucose sensors. To be implanted, cathodic and anodic enzymes have to be enough stable and resistant to physiological salts to be efficient several weeks or months in biological fluids.Here, I will focus my presentation on the enzymatic cathodic part. BODs and laccases are well known to be sensitive to high salt concentrations [3] and their stability on the electrode needs to be improved. Efforts in this direction allowed our team to identify the BOD from Bacillus pumilus with interesting features as a cathodic enzyme [4]. By using a sequence analysis approach, a new BOD was identified with very interesting features compared to other BODs which makes it of great interest to be used as a cathodic enzyme in biofuel cells.Particularly, in contrast to most BODs described, this new BOD is not inhibited but activated by several salts (up to 1,7 times). This characteristic makes this BOD very interesting considering the fact that all biological fluids contain relatively high levels of salts (such as 140mM NaCl in the blood for example). For this reason, we have compared the effect of various salts and their mechanisms on the enzymatic activity of BOD from Bacillus pumilus and the new BOD in solution and immobilized on electrode. Molecular modeling studies were also performed on both enzymes to decipher the mechanisms of activation/inhibition of different salts and more precisely the sodium chloride effects at the atomic level.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.