We identified and characterized the full-length cDNA sequences encoding two acetylcholinesterases (ClAChE1 and ClAChE2) and a salivary gland-specific cholinesterase (ClSChE) from the common bed bug, Cimex lectularius. All three cholinesterase genes (Clac1, Clace2 and Clsce) have conserved motifs, including a catalytic triad, a choline binding site and an acyl pocket. Phylogenetic analysis showed that ClAChE1 belongs to the insect AChE1 clade, whereas ClAChE2 belongs to the insect AChE2 clade. ClSChE was grouped into the clade containing all AChE1s, suggesting its paralogous relationship to ClAChE1. Transcription levels of Clace1 were higher than those of Clace2 in all tissues examined, including the central nervous system (CNS). In contrast, the Clsce transcript was not detected in the CNS but specifically found in the salivary gland in much higher levels (>3000 fold) than those of Clace1 and Clace2. Western blot analysis using anti-ClAChE antibodies in conjunction with activity staining revealed that ClAChE1 is more active than ClAChE2 whereas ClSChE has little enzyme activity. Three-dimensional structure modeling suggested that ClAChEs and ClSChE shared structural similarities, but had some differences in the residues forming the acyl pocket and oxyanion hole. The current findings should provide valuable insights into the evolution and functional diversification of insect cholinesterase.

• Keon Mook Seong(Department of Agricultural Biotechnology, Seoul National University)
• Young Ho Kim(Department of Agricultural Biotechnology, Seoul National University)
• Deok Ho Kwon(Research Institute for Agriculture and Life Sciences, Seoul National University)
• Si Hyeock Lee(Department of Agricultural Biotechnology, Seoul National University, Research Institute for Agriculture and Life Sciences, Seoul National University)