It has been previously suggested that human thioredoxin reductase activity is regulated by calcium. However, the activity of a purified form of human placental thioredoxin reductase was found to not be affected by mM concentrations of calcium, well above intra- and extracellular physiological levels. Furthermore, the suggestion that an E-F hand is present in Escherichia coli thioredoxin reductase is strongly contested. These current results suggest that human thioredoxin reductase is not regulated by calcium.
