Modification of wheat gluten with oxidative enzymes

Conventional enzymatic treatments in food processing are performed by using hydrolytic enzymes. The utilization of other types of enzymes, such as transglutaminase or oxidative enzymes, is continuously increasing. Transglutaminase (EC 2.3.2.13) catalyzes the reaction between glutamine and e.g lysine residues and creates new peptide linkages into and between the polypeptide chains of proteins. Oxidoreductases, like monophenol monooxygenase (EC 1.14.18.1), catechol oxidase (EC 1.10.3.1) and laccase (EC 1.10.3.2) may also modify proteins. Monophenol monooxygenase, tyrosinase, is known to act on tyrosine. It could be assumed that phenoloxidases may attack also other aromatic amino acids. VTT Biotechnology and Food Research has worked with laccases for several years and developed applications for different purposes. Applications in pulp and paper, textile, and chemical industry have been successful. Laccase is an ideal enzyme because it does not need any co-factors and it is active towards a variety of structurally different substrates. Laccase starts a radical reaction resulting polymerization. Concerning proteins this may include cross-linking. It has been reported recently that treatment with laccase improves the baking quality of flour (1). The aim here was to study the effects of laccases on the proteins of wheat gluten fraction.