Research Institute for Agriculture and Life Sciences, Seoul National University, 599 Gwanakno, Gwanakgu, Seoul 151-742, Republic of Korea.
Insect Biochem Mol Biol. 2013 Jan;43(1):47-53. doi: 10.1016/j.ibmb.2012.11.004. Epub 2012 Nov 17.
Most insects possess two different acetylcholinesterases (AChEs) (i.e., AChE1 and AChE2; encoded by ace1 and ace2 genes, respectively). Between the two AChEs, AChE1 has been proposed as a major catalytic enzyme based on its higher expression level and frequently observed point mutations associated with insecticide resistance. To investigate the evolutionary distribution of AChE1 and AChE2, we determined which AChE had a central catalytic function in several insect species across 18 orders. The main catalytic activity in heads was determined by native polyacrylamide gel electrophoresis in conjunction with Western blotting using AChE1- and AChE2-specific antibodies. Of the 100 insect species examined, 67 species showed higher AChE1 activity; thus, AChE1 was considered as the main catalytic enzyme. In the remaining 33 species, ranging from Palaeoptera to Hymenoptera, however, AChE2 was predominantly expressed as the main catalytic enzyme. These findings challenge the common notion that AChE1 is the only main catalytic enzyme in insects with the exception of Cyclorrhapha, and further demonstrate that the specialization of AChE2 as the main enzyme or the replacement of AChE1 function with AChE2 were rather common events, having multiple independent origins during insect evolution. It was hypothesized that the generation of multiple AChE2 isoforms by alternative splicing allowed the loss of ace1 during the process of functional replacement of AChE1 with AChE2 in Cyclorrhapha. However, the presence of AChE2 as the main catalytic enzyme in higher social Hymenoptera provides a case for the functional replacement of AChE1 with AChE2 without the loss of ace1. The current study will provide valuable insights into the evolution of AChE: which AChE has been specialized as the main catalytic enzyme and to become the main target for insecticides in different insect species.
大多数昆虫拥有两种不同的乙酰胆碱酯酶（AChE）（即 AChE1 和 AChE2；分别由 ace1 和 ace2 基因编码）。在这两种 AChE 中，AChE1 因其更高的表达水平和经常观察到的与杀虫剂抗性相关的点突变而被提议为主要的催化酶。为了研究 AChE1 和 AChE2 的进化分布，我们确定了在 18 个目（order）的几种昆虫物种中哪种 AChE 具有中心催化功能。头部的主要催化活性通过使用 AChE1 和 AChE2 特异性抗体的天然聚丙烯酰胺凝胶电泳结合 Western blot 来确定。在所检查的 100 种昆虫物种中，有 67 种物种表现出更高的 AChE1 活性；因此，AChE1 被认为是主要的催化酶。然而，在其余 33 种物种中，从古翅目到膜翅目，AChE2 主要表达为主要的催化酶。这些发现挑战了 AChE1 是除鳞翅目以外的昆虫中唯一主要的催化酶的普遍观点，并进一步表明，AChE2 作为主要酶的专业化或 AChE1 功能被 AChE2 取代是相当普遍的事件，在昆虫进化过程中有多个独立的起源。人们假设，通过选择性剪接产生的多个 AChE2 同工型允许在鳞翅目昆虫中用 AChE2 取代 AChE1 的功能过程中丢失 ace1。然而，在较高的社会性膜翅目昆虫中，AChE2 作为主要的催化酶存在，为在没有丢失 ace1 的情况下用 AChE2 取代 AChE1 的功能提供了一个案例。本研究将为 AChE 的进化提供有价值的见解：哪种 AChE 已专门化作为主要的催化酶，并成为不同昆虫物种中杀虫剂的主要靶标。
