Recombinant full-length human MEK4 was expressed by baculovirus in Sf9 insect cells using an N-terminal GST tag. Mitogen-activated protein kinase kinase 4 (MEK4 or MKK4) is a dual specificity kinase of the STE7 family that phosphorylates and activates JNK1 and -2 as well as p38. MKK4 preferentially phosphorylates the tyrosine residue of JNKs. ADP-Glo Kinase Assay is a luminescent kinase assay that measures ADP formed from a kinase reaction; ADP is converted into ATP, which is a substrate in a reaction catalyzed by Ultra-Glo Luciferase that produces light. The luminescent signal positively correlates with ADP amount and kinase activity. The assay is well suited for measuring the effects chemical compounds have on the activity of a broad range of purified kinases, making it ideal for both primary screening as well as kinase selectivity profiling. The ADP-Glo Kinase Assay can be used to monitor the activity of virtually any ADP-generating enzyme (e.g., kinase or ATPase) using up to 1mM ATP.