Notes: Cayman’s Glutaredoxin Fluorometric Activity Assay Kit provides a convenient method of measuring Grx activity in cell lysates and tissue samples. In this reaction, the substrate eosin-GS-BSA (self-quenched) is reduced by Grx, giving the fluorescent product eosin-GSH that can be detected at an emission wavelength of 560 nm. Grx becomes oxidized during the reaction and then reduced by glutathione to produce GSSG, which is recycled by a coupled reaction via glutathione reductase and NADPH (see Reaction Schematic image). The increase in signal is directly proportional to the Grx activity in the sample.