Inhibitors of oncogene product enzyme activity were sought as a prescreen for potential cancer chemopreventive agents. Purpurogallin, a polyphenol from Quercus sp. nutgall, was found to inhibit the tyrosine-specific protein kinase of the human erb-b oncogene product (epidermal growth factor receptor) for both autophosphorylation (IC50=27.5 μM) and phosphorylation of an exogenous substrate (IC50= 45.3 μM). An examination of enzyme kinetics indicated that purpurogallin is a competitive inhibitor of both ATP (K(i) = 54.9 μM for autophosphorylation, K(i) = 33.9 μM for phosphorylation of exogenous substrate) and the tyrosine-containing acceptor substrate poly(glutamate, alanine, tyrosine) 6:3:1 (K(i) = 83.7 μM).
|Original language||English (US)|
|Number of pages||4|
|State||Published - Jun 1 1999|
- Cancer chemopreventive agent
- Epidermal growth factor receptor
- Tyrosine-specific protein kinase inhibitor