Estevez_2018_Toxicology_410_73

Some effects of organophosphorus compounds (OPs) esters cannot be explained by action on currently recognized targets acetylcholinesterase or neuropathy target esterase (NTE). In previous studies, in membrane chicken brain fractions, four components (EPalpha, EPbeta, EPgamma and EPdelta) of phenyl valerate esterase activity (PVase) had been kinetically discriminated combining data of several inhibitors (paraoxon, mipafox, PMSF). EPgamma is belonging to NTE. The relationship of PVase components and acetylcholine-hydrolyzing activity (cholinesterase activity) is studied herein. Only EPalpha PVase activity showed inhibition in the presence of acetylthiocholine, similarly to a non-competitive model. EPalpha is highly sensitive to mipafox and paraoxon, but is resistant to PMSF, and is spontaneously reactivated when inhibited with paraoxon. In this papers we shows that cholinesterase activities showed inhibition kinetic by PV, which does not fit with a competitive inhibition model when tested for the same experimental conditions used to discriminate the PVase components. Four enzymatic components (CP1, CP2, CP3 and CP4) were discriminated in cholinesterase activity in the membrane fraction according to their sensitivity to irreversible inhibitors mipafox, paraoxon, PMSF and iso-OMPA. Components CP1 and CP2 could be related to EPalpha as they showed interactions between substrates and similar inhibitory kinetic properties to the tested inhibitors.