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Inhibition of oncogene product enzyme activity as an approach to cancer chemoprevention. Tyrosine‐specific protein kinase inhibition by purpurogallin from Quercus sp. Nutgall
Author(s) -
AbouKaram Mohamed,
Thomas Shier W.
Publication year - 1999
Publication title -
phytotherapy research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.019
H-Index - 129
eISSN - 1099-1573
pISSN - 0951-418X
DOI - 10.1002/(sici)1099-1573(199906)13:4<337::aid-ptr451>3.0.co;2-j
Subject(s) - autophosphorylation , biochemistry , tyrosine kinase , chemistry , enzyme , enzyme inhibitor , phosphorylation , biology , protein kinase a , signal transduction
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 (IC 50 = 27.5 µ M ) and phosphorylation of an exogenous substrate (IC 50 =45.3 µ M ). An examination of enzyme kinetics indicated that purpurogallin is a competitive inhibitor of both ATP ( K i = 54.9 µ M for autophosphorylation, K i = 33.9 µ M for phosphorylation of exogenous substrate) and the tyrosine‐containing acceptor substrate poly(glutamate, alanine, tyrosine) 6:3:1 ( K i = 83.7 µ M ). Copyright © 1999 John Wiley & Sons, Ltd.