Electron transferring dyes in the nitrate reductase reaction : non-toxic alternatives to methyl viologen

A range of electron-transferring agents (dyes) were screened for activity with the oxido-reductase, nitrate reductase, from either Pisum sativum or Aspergillus. Reducing equivalents could be transferred efficiently to both enzymes by methyl viologen. Pisum enzyme could also be effectively reduced by reduced Patent blue (food colouring E 131), curcumin (food colouring E 100) or, at lesser rates by Azure A. Aspergillus enzyme could be reduced at only low rates by curcumin, Patent blue and Bromophenol blue.