CHARACTERIZATION OF A TYROSINASE FROM AMANITA-MUSCARIA INVOLVED IN BETALAIN BIOSYNTHESIS

A tyrosinase was characterized from the betalain-containing pileus of the mushroom Amanita muscaria. The enzyme was located exclusively in t he coloured parts of the mushroom and hydroxylated tyrosine to 3:(3,4- dihydroxyphenyl)-alanine (DOPA), suggesting that it is involved in bet alain biosynthesis. The tyrosinase was not specific for tyrosine, and in addition to the monophenolase activity, the enzyme also oxidized di phenols to o-quinones (diphenolase activity). The native enzyme appear ed to be a heterodimer of two subunits with M(r)s of 27 000 and 30 000 , which is unusual for tyrosinases. Typical tyrosinase inhibitors such as tropolone, 2-mercaptobenzothiazole and benzoic acid strongly inhib ited the enzyme.