(A, B) MS-based ABPP of serine hydrolase activities in SW620 cells treated with DMSO or FAAH inhibitor. Shown in (A) are BIA 10-2474, BIA 10-2639, and PF04457845 (10 μM, 4 h, 37 °C). Shown in (B) are BIA 10-2474 and PF04457845 (50 μM, 24 h, 37 °C). Data are expressed as median SILAC ratio values for all isotopic peptide pairs quantified per protein from two biological replicates. (C) Confirmation of representative off-targets of BIA 10-2474 by gel-based ABPP of recombinantly expressed enzymes in HEK293T cells.