Flavonoids as inhibitors of LCK and FYN kinases

Phosphorylation of tyrosine residues constitutes a unique signaling pathway involved in regulation of most cellular processes responding to different extracellular stimuli.The enzymes that carry out this modification are tyrosine kinases.These enzymes enable the transfer of g-phosphate from ATP to the phenol -OH group of tyrosine on protein substrates.Development of specific and potent protein kinase inhibitors is important not only for treatment of diseases, but also as a tool to investigate the physiological roles of protein kinases.Flavonoids are biologically active polyphenol compounds naturally occurring in many plants.They are recognized as inhibitors of Fyn and Lck protein kinases, two representatives of the Src family of non-receptor kinases involved in T-cell signaling transport.In the described experiments, the inhibitory activity of flavonoids on Fyn and Lck kinases was monitored by the ELISA method.Myricetin showed the highest inhibitory effect, and no ATP-competitive mechanism of inhibition was observed on Fyn tyrosine kinase.The affinity of human Fyn and Lck for two different substrates, polypeptide polymer Poly Glu:Tyr (4:1) and peptide M3-01, was also tested.