TRANSCRIPTION OF THE TYROSINASE GENE IN STREPTOMYCES-MICHIGANENSIS DSM-40015 IS INDUCED BY COPPER AND REPRESSED BY AMMONIUM

Induction of tyrosinase activity in the actinomycin producer Streptomyces michiganensis requires a medium low in ammonium and ri ch in copper ions. Copper is not only an essential part of the tyrosinase enzyme but it is also required for the induction of the gene at the level of transcription. Addition of copper, effective in both young and old cultures, specifically induces tyrosinase, which under optimal conditions may become the major newly synthesized protein. Ammonium represses tyrosinase formation at the level of transcription. Once repressed, tyrosinase biosynthesis cannot be induced by copper.