N-acetyl-6-hydroxytryptophan oxidase, a developmentally controlled phenol oxidase from Aspergillus nidulans

J Gen Microbiol. 1990 Sep;136(9):1725-30. doi: 10.1099/00221287-136-9-1725.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Aspergillus nidulans / enzymology*
  • Binding, Competitive
  • Copper / pharmacology
  • Enzyme Stability
  • Hot Temperature
  • Molecular Sequence Data
  • Monophenol Monooxygenase / chemistry*
  • Monophenol Monooxygenase / isolation & purification
  • Phenols / metabolism*
  • Substrate Specificity

Substances

  • Phenols
  • Copper
  • N-acetyl-6-hydroxytryptophan oxidase
  • Monophenol Monooxygenase

Associated data

  • PIR/B33069