Abstract
Adenylate kinase (AK) is a ubiquitous and abundant enzyme catalyzing the phosphoryl transfer between two adenosine diphosphate (ADP) molecules to yield adenosine triphosphate (ATP) and adenosine monophosphate (AMP). The enzyme has gained much attention recently because it can be used as a cell marker to replace ATP in the luciferase-based bioluminescence assay. The use of AK has the potential to offer much greater sensitivity than ATP measurement and is more reliable in determining cell numbers. AK can be used to regenerate ATP from the AMP produced in the luciferase reaction. This creates a cyclic loop of ATP amplification and can significantly enhance the bioluminescence assay sensitivity.