NEW POSTER: Crosslinking of beta-casein with T. reesei tyrosinase and S. mobaraense transglutaminase

Wednesday, 29 October 2008 16:52

Monogioudi et al. investigated the enzymatic crosslinking of β-casein isolated from milk. In the study both a novel tyrosinase as well as well-known transglutaminase were used. Transglutaminase is an enzyme capable of crosslinking proteins via lysine and glutamine residues. This enzyme has been extensively studied on different food matrices including milk products. Tyrosinase is an oxidative enzyme, known to catalyze the oxidation of the phenolic ring of tyrosine residues to the corresponding quinones which then in turn can create crosslinks between proteins. About 25 % of the milk proteins are β-casein. β-casein contains lysine, glutamic acid and tyrosine amino acids and is thus a potential substrate for these two different types of enzymes.

In this work cross-linking of β-casein by fungal Trichoderma reesei tyrosinase (TrTyr) and microbial transglutaminase (TGase) was studied by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-Page) and size exclusion chromatography (SEC) equipped with UV/VIS and multi-angle light scattering (MALLS) detectors to determinate the molecular masses of the cross-linked products. Three different enzyme dosages (10, 100 and 1000 nkat/g) and reaction times (2, 6 and 24 h) were used to optimize the enzymatic reaction conditions at 40 °C. Oxygen consumption measurement was used to verify the reactivity of TrTyr on β-casein. Cross-linking with TrTyr resulted in the formation of coloured products and hence the progress of the enzymatic reaction was also visually followed as a function of time. The molecular masses of the cross-linked products ranged from 500 to 1700 kDa for TrTyr and from 500 to 1500 kDa for TGase.

Reference: Monogioudi, E., Creusot, N., Kruus, K., Gruppen, H., Mattinen, M-L., Buchert, J. Cross-linking of β-casein with Trichoderma reesei tyrosinase and Streptoverticillium mobaraense transglutaminase, COST 928 Workshop, Istanbul 15 - 17 October, 2008.

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