A Tyrosine Kinase Inhibitor. An isoflavonoid derived from soy products. Genistein inhibits protein tyrosine kinases, including the EGF receptor kinase (IC50= 2.6 uM). The inhibition is competitive with respect to ATP and non-competitive with respect to the phosphate acceptor. It has a trivial effect on the activity of 5/PKA and 5/PKC (IC50 > 350 uM). In addition, Genistein inhibits Topoisomerase II activity, cause cell cycle arrest and apoptosis in Jurkat T-leukemia cells. It down regulates the transcription of genes involved in angiogenesis, and inhibit the action of GABA on recombinant GABA-A receptors. Genistein also inhibits tumor cell proliferation and induces tumor cell differentiation. Protein Kinase Inhibitors and Activators; Tyrosine Kinase Inhibitor. Cell Signaling Activators and Inhibitors; Topoisomerase Inhibitors.