Modifications of amino acids during ferulic acid-mediated, laccase-catalysed cross-linking of peptides.

Steffensen CL, Stensballe A, Kidmose U, Degn PE, Andersen ML, Nielsen JH.

Department of Food Science, Faculty of Agricultural Sciences, Aarhus University, Research Centre Foulum, Tjele, Denmark.


Mass spectral analysis demonstrated oligomerization of peptides that had been subjected to oxidation catalysed by Trametes (Coriolus) versicolor laccase. Peptide oligomerization occurred only when cysteines or tyrosines were present in the peptides. MS/MS confirmed the cross-linking in tyrosine-containing peptides to be located between tyrosine residues. Ferulic acid mediated oligomerization of cysteine-containing peptides, but prevented cross-linking of tyrosines when used in the same concentration as the peptides. This suggests an antioxidative effect of ferulic acid in relation to tyrosine oxidation, although incorporation of ferulic acid into peptide oligomers was found in some of the tyrosine-containing peptides. No other modifications to amino acid residues by laccase-catalysed oxidation were observed by mass spectroscopy. Thus, it is suggested that oxidative modifications of other amino acids observed in proteins oxidized by laccase are not major reaction products of laccase-catalysed oxidation.

PMID: 19905979 [PubMed – indexed for MEDLINE]