Summary: We have purified a specific phenol oxidase which is produced during conidiophore development in the fungus . Two active forms (A and B) have molecular masses of 50 and 48 kDa respectively; they have identical N-termini (24 residues). We have analysed the metal ion content of the B form; it is unusual in consisting of one zinc and two copper atoms per molecule. A temperature-sensitive mutant () produces a thermolabile enzyme, implying that is the structural locus. The natural substrate of the enzyme is -acetyl-6-hydroxytryptophan, but it can be assayed colorimetrically or polarographically using hydroquinone monomethyl ether (HME) as substrate. It will also oxidize -cresol, but not tyrosine, 3,4-dihydroxyphenylalanine or -methoxyphenol. Colour development with HME substrate is strongly enhanced by high ammonium ion concentrations. Activity against HME is inhibited by 2,3-dihydroxynaphthalene, phenylhydrazine, diethyl dithiocarbamate and 8-hydroxyquinolene.


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