Cell Biolabs’ OxiSelect™ Glutathione Reductase Assay Kit is a quantitative assay for measuring glutathione reductase activity within plasma, erythrocytes, tissues, and cell lysates. Glutathione reductase activity is defined as 1 unit of enzyme reducing 1 µmole oxidized glutathione (GSSG) per minute at pH 7.6 and 25ºC. The kit employs a simple enzymatic recycling reaction for glutathione quantification where the reduction of a chromagen is correlated to glutathione reductase enzymatic activity.