Human PON1 (h-PON1) is a Ca2+-dependent serum enzyme and can hydrolyze (and inactivate) a wide range of substrates. It is a multifaceted enzyme and exhibit anti-inflammatory, anti-oxidative, anti-atherogenic, anti-diabetic, anti-microbial, and organophosphate (OP)-detoxifying properties. Thus, h-PON1 is a strong candidate for the development of therapeutic intervention against these conditions in humans. Insufficient hydrolyzing activity of native h-PON1 against desirable substrate affirms the urgent need to develop improved variant(s) of h-PON1 having enhanced activity. Production of recombinant h-PON1 (rh-PON1) using an Escherichia coli expression system is a key to develop such variant(s). However, generation of rh-PON1 using E. coli expression system has been elusive until now because of the aggregation of over-expressed rh-PON1 protein in inactive form as inclusion bodies (IBs) in the bacterial cells. In this study, we have over-expressed rh-PON1((wt)) and rh-PON1((H115w,R192K)) proteins as IBs in E. coli, and refolded the inactive enzymes present in the IBs to their active form using in vitro refolding. The active enzymes were isolated from the refolding mixture by ion-exchange chromatography. The catalytic properties of the refolded enzymes were similar to their soluble counterparts. Our results show that the pure and the active variant of rh-PON1 enzyme having enhanced hydrolyzing activity can be produced in large quantities using E. coli expression system. This method can be used for the industrial scale production of rh-PON1 enzymes and will aid in developing h-PON1 as a therapeutic candidate. (C) 2015 Elsevier Inc. All rights reserved.