title: Structure-activity relationships of various amino-hydroxy-benzenesulfonic acids and sulfonamides as tyrosinase substrates.
abstract: BACKGROUND
  o-Aminophenols have been long recognised as tyrosinase substrates. However their exact mode of interaction with the enzyme's active site is unclear. Properly vic-substituted o-aminophenols could help gain some insight into tyrosinase catalytic mechanism.
  
  
  METHODS
  Eight vic-substituted o-aminophenols belonging to two isomeric series were systematically evaluated as tyrosinase substrates and/or activators and/or inhibitors, by means of spectrophotometric techniques and HPLC-MS analysis. Some relevant kinetic parameters have also been obtained.
  
  
  RESULTS
  Four o-aminophenolic compounds derived from 3-hydroxyorthanilic acid (2-amino-3-hydroxybenzenesulfonic acid) and their four counterparts derived from the isomeric 2-hydroxymetanilic acid (3-amino-2-hydroxybenzenesulfonic acid) were synthesised and tested as putative substrates for mushroom tyrosinase. While the hydroxyorthanilic derivatives were quite inactive as both substrates and inhibitors, the hydroxymetanilic compounds on the contrary all acted as substrates for the enzyme, which oxidised them to the corresponding phenoxazinone derivatives.
  
  
  CONCLUSIONS
  Based on the available structures of the active sites of tyrosinases, the different affinities of the four metanilic derivatives for the enzyme, and their oxidation rates, we propose a new hypothesis regarding the interaction between o-aminophenols and the active site of tyrosinase that is in agreement with the obtained experimental results.
authors: Dipartimento di Scienze e Tecnologie Biomediche, Università di Cagliari, Cittadella Universitaria, 09042 Monserrato (CA), Italy. rescigno@unica.it
authors: Antonio
authors: A
authors: Rescigno
authors: Frédéric
authors: F
authors: Bruyneel
authors: Alessandra
authors: A
authors: Padiglia
authors: Francesca
authors: F
authors: Sollai
authors: Andrea
authors: A
authors: Salis
authors: Jaqueline
authors: J
authors: Marchand-Brynaert
authors: Enrico
authors: E
authors: Sanjust