A COMMENT ON THE ABSENCE OF CALCIUM REGULATION OF HUMAN THIOREDOXIN REDUCTASE

It has been previously suggested that human thioredoxin reductase acti vity 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 conteste d. These current results suggest that human thioredoxin reductase is n ot regulated by calcium.