RT Journal Article SR Electronic(1) A1 Birse, Charles E. A1 Clutterbuck, A. JohnYR 1990 T1 N-Acetyl-6-hydroxytryptophan oxidase, a developmentally controlled phenol oxidase from Aspergillus nidulans JF Microbiology, VO 136 IS 9 SP 1725 OP 1730 DO https://doi.org/10.1099/00221287-136-9-1725 PB Microbiology Society, SN 1465-2080, AB We have purified a specific phenol oxidase which is produced during conidiophore development in the fungus Aspergillus nidulans. 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 (ivoB192) produces a thermolabile enzyme, implying that ivoB is the structural locus. The natural substrate of the enzyme is N-acetyl-6-hydroxytryptophan, but it can be assayed colorimetrically or polarographically using hydroquinone monomethyl ether (HME) as substrate. It will also oxidize p-cresol, but not tyrosine, 3,4-dihydroxyphenylalanine or o-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., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-136-9-1725