Differentiation of tyrosine hydroxylase and phenol oxidase after electrophoresis

Tyrosine hydroxylase and phenoloxidase differ in that tyrosine hydroxylase (E.C.1.14.16.2) can hydroxylate tyrosine into -o-diphenol, but cannot oxidize the -o-diphenol, whereas phenoloxidase (E.C.1.14.18.1) is capable of oxidizing -o-diphenol to quinone. This difference can be exploited by staining tyrosine hydroxylase activity with a substrate-PMS-NBT method and staining the phenoloxidase with a dopamine-MBTH method. Based on the staining properties of the bands separated after electrophoresis, tyrosine hydroxylase has been differentiated from phenoloxidase in the silkworm Bombyx mori and the occurrence of tyrosine hydroxylase has been reported for the first time in this worm.