[30] Use and specificity of genistein as inhibitor of protein-tyrosine kinases

Genistein—that is 5,7-dihydroxy-3-(4-hydroxyphenyl)-4H-1-benzopyran-4-one;4',5,7-trihydroxyisoflavone, has been isolated as an inhibitor of tyrosine phosphorylation from a culture broth of Pseudomonas. This compound has been shown to inhibit the activity of tyrosine kinases, such as the epidermal growth factor (EGF) receptor and pp60 s'c, but scarcely to inhibit the activity of serine and threonine kinases such as cAMPdependent protein kinase. Therefore, genistein is a good tool to elucidate cellular processes mediated by tyrosine phosphorylation, in particular, the molecular cascades involved in cellular proliferation, transformation, and differentiation.