Human butyrylcholinesterase (HuBChE) is of particular interest because it hydrolyzes a wide range of toxic compounds such as cocaine, succinylcholine and carbamate pesticides. In this study, HuBChE was purified from human plasma using polyethylene glycol (PEG), differential precipitation and ion exchange chromatographic procedures. Purification resulted in a homogeneous enzyme preparation with a 5575-fold purification, and specific activity of 485 U/mg proteins with a reasonable final yield (36%). The final purified HuBChE showed a single electrophoresis band (85 kDa) on SDS-PAGE. Purified enzyme was stabilized with glycerol, PEG, and ammonium sulphate. Kinetic studies of the enzyme showed high affinity for butyrylthiocholine (k(m) = 18 +/- 5 muM) and low affinity for acetylthiocholine (k(m) = 83 +/- 12 muM), paraoxon, parathion, and tetra monoisopropyl pyrophosphomide all inhibited the enzyme with IC50 of 2.8 +/- 0.8, 22 +/- 2 and 55 +/- 4 muM, respectively. The procedure introduced is inexpensive, simple and comparable to procainamide affinity column chromatography. This procedure can provide large quantities of purified enzyme with acceptable stability. (C) 2003 Elsevier Ltd. All rights reserved.