Competitive ABPP of (MIDA)boronates in PC3 cell lysates. A, Gel-based ABPP analysis of (MIDA)boronates in the soluble proteome of PC3 cells. The proteome was treated with either DMSO or compounds 7a–j (20 μM) for 2 h, then treated with FP-Rh (1.0 μM) for 30 min. Labeled serine hydrolases were resolved by SDS-PAGE and analyzed by fluorescence gel imaging. B, Gel-based ABPP analysis of 7j (1.0 nM–100 μM) and DMSO in the soluble fraction of PC3 cells showing dose-dependent inhibition of ABHD10 and ACOT1/2. C, ABPP-SILAC analysis of 7j at 25 μM (heavy) versus DMSO (light) in whole PC3 cell proteomic lysates showing inhibition of ABHD10, CPVL and, to a lesser extent, ACOT1/2. Data are presented as the mean ± standard deviations of heavy/light ratios for multiple unique peptides from each serine hydrolase.