Bovine serum albumin interacts with bacterial luciferase

Bovine serum albumin (BSA) affects the amount of light obtained from bacterial luciferase by competing with luciferase for one of the luciferase substrates, the aldehyde. At low aldehyde concentrations BSA behaves as an inhibitor, but at high aldehyde concentrations BSA relieves substrate inhibition. BSA reversibly binds decanal with a Ksi = 3.36 mumol/l, approximately half the affinity of luciferase for decanal (KM = 1.5 mumol/l). BSA also increased the rate of intermediate II dark decay. The data suggest that this involves a direct protein-protein (BSA-luciferase) interaction.