Detect active serine protease enzymes with the FAM-Spacer-Phe-CMK Green FLISP Assay. This in vitro assay employs the green fluorescent label carboxyfluorescein (FAM), which is linked to a 6 carbon spacer, phenylalanine, and a chloromethyl ketone (CMK) reactive group, forming the fluorescent inhibitor probe, FAM-Spacer-Phe-CMK. The 6 carbon hexanoic spacer is designed to reduce steric hindrance of the single amino acid phenylalanine target. FAM-FLISP labels active chymotrypsin-like serine proteases in living cells. Analyze samples using fluorescence microscopy, fluorescence plate reader, or flow cytometry.