title: N-acetyl-6-hydroxytryptophan oxidase, a developmentally controlled phenol oxidase from Aspergillus nidulans.
abstract: 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.
authors: Department of Genetics, Glasgow University, UK.
authors: C E
authors: CE
authors: Birse
authors: A J
authors: AJ
authors: Clutterbuck
mesh_terms: D000595:Amino Acid Sequence; D001233:Aspergillus nidulans / Q000201:enzymology*; D001667:Binding, Competitive; D003300:Copper / Q000494:pharmacology; D004795:Enzyme Stability; D006358:Hot Temperature; D008969:Molecular Sequence Data; D014442:Monophenol Monooxygenase / Q000737:chemistry* / Q000302:isolation & purification; D010636:Phenols / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D010636:Phenols; D003300:Copper; C067267:N-acetyl-6-hydroxytryptophan oxidase; D014442:Monophenol Monooxygenase