Interaction of the serine hydrolase KIAA1363 with organophosphorus agents: Evaluation of potency and kinetics

Abstract

Oxons are bioactive metabolites of organophosphorus insecticides (OPs) that covalently inactivate serine hydrolases. KIAA1363 is one of the most abundant serine hydrolases in mouse brain. Although the physiological consequences related to the inhibition of KIAA1363 due to environmental exposures to OPs are poorly understood, the enzyme was previously shown to have a role in the detoxification of oxons. Here, we overexpressed human KIAA1363 and CES1 in COS7 cells and compared the potency of inhibition (IC50s, 15 min) of KIAA1363 and CES1 by chlorpyrifos oxon (CPO), paraoxon (PO), and methyl paraoxon (MPO). The order of potency was CPO > PO ≫ MPO for both enzymes. We also determined the bimolecular rate constants (kinact/Ki) for reactions of CPO and PO with KIAA1363 and CES1. KIAA1363 and CES1 were inactivated by CPO at comparable rates (4.4 × 106 s−1M−1 and 6.7 × 106 s−1M−1, respectively), whereas PO inactivated both enzymes at slower rates (0.4 × 106 s−1M−1 and 1.5 × 106 s−1M−1, respectively). Finally, the reactivation rate of KIAA1363 following inhibition by CPO was evaluated. Together, the results define the kinetics of inhibition of KIAA1363 by active metabolites of agrochemicals and indicate that KIAA1363 is highly sensitive to inhibition by these compounds.

Activity-based protein profiling of rice (Oryza sativa L.) bran serine hydrolases

“…In the gel-based ABPP, the two major signals which are inhibited by pre-incubation with PMSF in in-gel fluorescence scanning are, therefore, serine proteases. In our competitive ABPP assay, it was also observed that many of the detected SHs are sensitive towards commercial agrochemicals, paraoxon, and profenofos, which are the potent esterase and acetylcholinesterase inhibitors respectively 45,47 . The gel-based competitive ABPP results revealed the presence of many active esterases/lipases in the RB proteome.…”

“…The labeling of active serine hydrolases was done using 2 µM FP-Rh at pH 8.0 because the optimal SHs labeling was observed at this pH 8.0 in the complex protein lysates 44 . The organophosphate or -phosphonate compounds as well as carbamate compounds, are the potent SHs inhibitors and have been experimentally proven in competitive ABPP assay in the animal, plant, and archaea model systems 45 – 47 . To get more insight into the specificity and selectivity of rice bran SHs, we performed in vitro competitive ABBP with known serine hydrolase inhibitors such as PMSF, paraoxon, and profenofos.…”

KIAA1363 affects retinyl ester turnover in cultured murine and human hepatic stellate cells

“…Furthermore, KIAA1363 knockdown in human prostate PC3 cells resulted in reduced tumor growth in a mouse xenograft model, suggesting that KIAA1363 is involved in protumorigenic ether lipid signaling ( 23 ). (ii) Two independent groups reported KIAA1363 to be involved in the detoxification of organophosphates, by metabolizing low levels of the insecticide metabolite chlorpyrifos oxon in the brain ( 35 , 36 ). (iii) Ishibashi et al.…”

NAD(P)‐dependent steroid dehydrogenase‐like protein and neutral cholesterol ester hydrolase 1 serve as novel markers for early detection of gastric cancer identified using quantitative proteomics

“…NCEH1 also hydrolyzes 2‐acetyl monoalkylglycerol, a metabolic intermediate in the ether lipid pathway to form alkyl‐LPA. Moreover, NCEH1 may also hydrolyze exogenous organophosphorus compounds during organ detoxification 25 . NCEH1 is overexpressed in a variety of aggressive human cancer cell lines and primary tumors 20‐23 .…”