The present invention provides an arsenite oxidase enzyme modified to prevent translocation by modification of a translocation signal sequence. A microorganism modified to express the heterologous arsenite oxidase enzyme is also provided by the invention, together with a device for detecting the presence of arsenite in a sample.

The present invention is a device for detecting the presence of an analyte in a sample. The device comprises (i) at least one electrode, (ii) an oxidase enzyme, and (iii) first and second redox mediators.

The present invention provides a device for detecting the presence of an analyte in a sample, said device comprising (i) at least one electrode, (ii) a oxidase enzyme, and (iii) first and second redox mediators.