Interaction of mushroom tyrosinase with aromatic amines, o-diamines and o-aminophenols.
3-Amino-L-tyrosine was found to be a substrate of mushroom tyrosinase, contrary to what had previously been reported in the literature. A series of amino derivatives of benzoic acid were tested as substrates and inhibitors of the enzyme. 3-Amino-4-hydroxybenzoic acid, 4-amino-3-hydroxybenzoic acid and 3,4-diaminobenzoic acid were oxidized by this enzyme, as previously reported for Neurospora crassa tyrosinase, but 4-aminobenzoic acid and 3-aminobenzoic acid were not. Interestingly, 3-amino-4-hydroxybenzoic acid was oxidized five times faster than 4-amino-3-hydroxybenzoic acid, confirming the importance of proton transfer from the hydroxyl group at C-4 position. All compounds inhibited the monophenolase activity but their effect on the diphenolase activity was small or negligible. 3-Amino-4-hydroxybenzoic acid was a stronger inhibitor than 4-amino-3-hydroxybenzoic acid, indicating their different binding affinity to the oxy form of the enzyme. Both, however, were weaker inhibitors than 3-amino-L-tyrosine, 4-methoxy-o-phenylenediamine and 3,4-diaminobenzoic acid, which was the strongest inhibitor from among the compounds tested. These results show that the relative positioning of the amino group and the hydroxy group in o-aminophenols with respect to the side chain is important both for binding to the dicopper center and for catalysis.
Institute of Chemistry, University of Opole, Ul. Oleska 48, 45-052 Opole, Poland.
Beata
B
Gasowska
Paweł
P
Kafarski
Hubert
H
Wojtasek
D000363:Agaricales / Q000201:enzymology*; D000588:Amines / Q000378:metabolism*; D000627:Aminophenols / Q000378:metabolism*; D003959:Diamines / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D011485:Protein Binding
D000588:Amines; D000627:Aminophenols; D003959:Diamines; D014442:Monophenol Monooxygenase; D010100:Oxygen