Chemical modification of beta-lactoglobulin by quinones

Abstract

The avarone/avarol quinone/hydroquinone couple. as well as their derivatives show considerable antitumor activity. In this work, covalent modifications of beta-lactogglobulin. isolated from cow milk by avarone, its model compound 2-tert-butyl-1,4-benzoquinone. and several of their alkylthio derivatives were studied. The techniques applied for as-saying the modifications were: UV/VIS spectrophotometry, SDS PAGE and isoelectrofocusing. The results of the SDS PAGE suggest that polymerisation of the protein occurs. The shift of the pI of the protein upon modification toward lower values indicates that lysine amino groups are the principal site of die reaction of beta-lactoglobulin with the quinones.

Hinonsko/hidrohinonski par avaron/avarol i njihovi derivati pokazuju značajnu antitumorsku aktivnost. U ovom radu proučavane su kovalentne modifikacije β-laktoglobulina, izolovanog iz kravljeg mleka, avaronom, njegovim model-jedinjenjem 2-tert-butil-1,4-benzohinonom i njihovim alkiltio-derivatima. Za ispitivanje modifikacija korišćene su UV/VIS spektrofotometrija, SDS PAGE i izoelektrofokusiranje. Rezultat SDS PAGE ukazuje da se protein polimerizuje. Pomeranje pI vrednosti proteina nakon modifikacije ka nižim vrednostima pokazuje da su amino grupe lizina glavna mesta reakcije β-laktoglobulina sa hinonima.