In cancer cell lines, purines are predominantly synthesized through a multi-enzyme complex called the purinosome. This study investigates if there is a correlation between the number of enzyme copies within the purinosome and their individual activities. We developed a workflow to label purinosome enzymes with an affinity tag using the CRISPR-Cas9 genome editing technology to quantify pathway enzymes in the complex and determine the stoichiometric ratios between enzyme pairs by fluorescence microscopy.