Study on the Polymerization and Mechanism of Amino Acid Catalyzed by Laccase

Abstract

ABSTRACT Laccase-catalyzed coloration toward wool was carried out and the K/S of wool fabric dyed was much higher than raw wool, presenting a claybank color. On this basis, the reaction mechanism is elucidated using tyrosine, tryptophan and the mixture as substrates. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and LC-MS as well as FT-IR measurements were used to study the reactions. The results indicate that the laccase-catalyzed reaction of tyrosine monomer, tyrosine monomer and the mixture, respectively, generates free radicals, including phenoxy radical and benzene radicals, pyrrolidine radical. The coupling reaction can occur between two free radicals, and further the Michael addition reaction occurs between benzene radicals with monomer another tyrosine. In view of the tan polytyrosine and rufous polytryptophan, as well as the higher content of tyrosine than tryptophan, the oxidation coupling reaction of tyrosine residue predominates over that of tryptophan residue in the process of laccase-catalyzed coloration toward wool.