Effects of Selenite Ions on a Luminescence Enzymatic System

Abstract

This paper elucidates biochemical and physicochemical aspects of toxicity of a redox-active compound in organisms. Sodium selenite (Na₂SeO₃) was chosen as a model redox-active compound; a coupled enzymatic system from luminous marine bacteria was applied to imitate a biochemical process. We demonstrated that Na₂SeO₃ suppressed bioluminescence of the enzyme system; the effective inhibition concentration was 10^–2 M. Besides that, Na₂SeO₃ decreased the content of reactive oxygen species (ROS) in aqueous solutions (enzyme-free media) at >10^–3 M. Addition of enzymes and their substrates to these solutions enhanced this decrease. Correlations between dependencies of the ROS content and bioluminescence intensity on the concentration of Na₂SeO₃ were positive and high, confirming the ROS involvement in the bioluminescence suppression in Na₂SeO₃ solutions. Hence, we observed the disturbance of the native biochemical oxidative functions of dissolved oxygen derivatives under exposure to redox-active toxicants. The effects of Na₂SeO₃ on the bacterial enzyme system should be further compared with those on bacterial cells, which are traditionally used as a toxicity bioassay. Additionally, the use of natural microorganisms is perspective due to their ability of redox transformation of toxic selenium oxoanions to elemental selenium. This ability is important as it provides: (1) natural detoxification of water ecosystems, and (2) biosynthesis of selenium nanoparticles.