Action of 3 tyrphostin derivatives on casein kinase II from rat liver.

AIM: To study the action of tyrphostin on casein kinase (CK) II. METHODS: CK II was partially purified from rat livers by sequential DE52 and heparin-Sepharose chromatography. CK II activity was assayed by incubating CK II with dephosphorylated casein and [gamma-32P]ATP. RESULTS: AG34 inhibited the activity of CK II with IC50 33 (27-41) mumol.L-1. Both AG372 (121 mumol.L-1) and AG1112 (150 mumol.L-1) displayed inhibitory effects on the activity of CK II. Kinetic studies of AG34 on CK II showed that it was noncompetitive with casein and ATP. CONCLUSION: AG34, AG372, and AG1112 were potent inhibitors of CK II, and the inhibitory action of AG34 was noncompetitive with casein and ATP.