Figure 9.

KIT-catalyzed tyrosine kinase activity in cell-free condition. Catalytically active rhKIT was reacted with poly(Glu,Tyr 4:1) peptide as an exogenous substrate in the presence of BPT. (A) In vitro kinase activity as the count per minute (cpm) by incorporating [³²P] from [γ-³²P]ATP to the peptide substrate. Data are mean ± SEM. *P < 0.05 vs. rhKIT alone. (B) rhKIT kinetics with varying concentrations of ATP as the absorbance change at 450 nm per minute (△A₄₅₀/min) by ELISA. Symbols are KIT activity in the presence of 10 μM (solid triangle) or 0.1 μM of BPT (open circle) and in the absence of BPT (solid circle). Data are mean values.