INACTIVATION EXPERIMENTS ON THE DOPA FACTOR

P. VAN DUIJN ¹

¹ Department of Biochemistry of the Laboratory for Pathology, University of Leiden, (Netherlands)

1. It is demonstrated that the interpretation of the histochemical dopa reaction, discovered by Bloch, correlated with mammalian melanogenesis in vivo has been greatly influenced by the analogy of the tryosinase-tyrosin reaction in vitro with the same process.

2. Repeating Bloch's histochemical pretreatment experiments on fixed tissue proved that the extreme lability found by Bloch must be attributed to detachment of the factor from the section or insufficient control of pH of the pretreatment solution.

3. Sufficient lability remains to be in line with an enzymatic nature, though classifying the factor in the realm of copper containing enzymes must be considered premature for lack of comparable data in the extract enzymological field.

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