PARTIAL-PURIFICATION AND CHARACTERIZATION OF TRIATOMA-INFESTANS HEAD ACETYLCHOLINESTERASE

A cholinesterase (ChE) from the heads of Triatoma infestans was purified partially by sodium deoxycholate solubilization and by ammonium sulphate and acetone fractionation. The enzyme was purified 14 fold with a yield of 78%. The purified ChE was considered to be an acetylcholinesterase (AChE) based on its substrate specificity, its response to selective inhibitors, the pH sensitivity of its hydrolysis of acetylcholine (ACh) and its inhibition by excess substrate. The purified fraction was shown to be free of butyrylcholinesterase and eserine-resistant esterases which were present in crude homogenates. Disc electrophoresis revealed three interconvertible forms of AChE in the purified enzyme. AChE from T. infestans hydrolyses ACh and its thio-analogue (ATC) at higher rates than other choline esters tested. Maximal velocity for the hydrolysis of ACh by this enzyme was shown at pH 3.3 and pH 7.2. With ATC a Km of 3.3 × 10-5 M was obtained. The organophosphates were shown to be potent inhibitors of the purified AChE. © 1979.