We present here,
method development for an enzyme inhibition assay for the ectonucleotidase,
CD39. Ectonucleotidases are plasma membrane-bound enzymes with extracellular
active sites that metabolise nucleotides to nucleosides and are crucial for
maintaining immune homeostasis. Blockage of this pathway may promote
anti-tumour immunity. 

Two assay methods were identified as potential routes to
measure CD39 enzymatic activity; a colourimetic phosphate detection assay,
where free phosphate combines with reagents to produce a green dye, and a
nucleotide displacement method, using fluorescence polarisation. Both methods
were evaluated for robustness and reproducibility.