Determination of the DNA sequences of acetylcholinesterase and butyrylcholinesterase from cat and demonstration of the existence of both in cat plasma

Cat serum contains 0.5 mg/L of butyrylcholinesterase (BChE, EC 3.1.1.8) and 0.3 mg/L of acetylcholinesterase (AChE, EC 3.1.1.7); this can he compared with 5 mg/mL and < 0.01 mg/L, respectively, in human serum. Cat BChE differed from human BChE in the steady-state turnover of butyrylthiocholine, having a 3-fold higher k(cat) and 2-fold higher K-m and K-ss values. Sequencing of threat BCHE cDNA revealed 70 amino acid differences between cat and human BChE, three of which could account fur these kinetic differences. These amino acids, which were located in the region of the active site, were Phe398Ile, Pro285Leu, and Ala277Leu (where the first amino acid was found in human and the second in cat). Sequencing genomic DNA for cat and human ACHE demonstrated that there were 33 amino acid differences between the car and human AChE enzymes, but. that there were no differences in the active site region. In addition, a polymorphism in intron 3 of the human ACHE gene was detected, as well as a silent polymorphism at Y116 of the cat ACHE gene. BIOCHEM PHARMACOL 60;4:479-487, 2000. (C) 2000 Elsevier Science Inc.