BIOGENESIS OF BETALAINS - PURIFICATION AND PARTIAL CHARACTERIZATION OF DOPA 4,5-DIOXYGENASE FROM AMANITA-MUSCARIA

3,4-Dihydroxyphenylalanine 4,5-dioxygenase, a central enzyme in the biogenesis of betalains, has been purified from the mushroom Amanita muscaria. Like other extradiol-cleaving dioxygenases, this enzyme is an oligomer; however, DOPA 4,5-dioxygenase is composed of varying number of an identical subunit of M(r) 22 000. It is inhibited by cyanide, diethylpyrocarbonate and various nitrogen-containing ion chelating agents. The enzyme does not exhibit a strict specificity for DOPA. Other p-dihydric aromatic compounds such as dopamine and catechol are also converted to alpha-hydroxymuconic epsilon-semialdehyde derivatives. This is the first report of an enzyme involved in the metabolism of betalain pigments.