All serine hydrolases possess a common catalytic mechanism that involves activation of a conserved serine nucleophile for attack on a substrate ester/thioester/amide bond to form an acylenzyme intermediate, followed by water-catalyzed hydrolysis of this intermediate to liberate the product. The greatly enhanced nucleophilicity of the catalytic serine renders it susceptible to covalent modification by many types of electrophiles, including fluorophosphonates (FPs) and aryl phosphonates, sulfonyl fluorides, and carbamates (Alexander and Cravatt, 2005; Jessani et al., 2005; Okerberg et al., 2005) . FPs are highly reactive and provide broad coverage, with the capacity to react with nearly all essential serine hydrolases (Bachovchin et al., 2010) . Therefore, they are ideal reagents to use for ABPP of serine hydrolases (Liu et al., 1999; Patricelli et al., 2001) . However, certain serine proteases displayed restricted substrate selectivities that reduce their labeling with FPs. To address this limitation of FPs, selective inhibitors (e.g., carbamates, triazole ureas) have been introduced to probe the function of individual serine hydrolase in biological systems (Bachovchin et al., 2010; Adibekian et al., 2011) .