Recombinant full-length human BLK was expressed by baculovirus in Sf9 insect cells using a N-terminal GST tag. BLK, also known as B lymphoid kinase, is a 55 kd tyrosine kinases with a SH3, SH2 and catalytic domains that contain consensus sequences of the src protein tyrosine kinase family. BLK is expressed specifically in the B cell lineage and plays a role in signal transduction pathway that is restricted to B lymphoid cells. 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.