Khajehali et al. found this modification in all three OP strains but not all clones. This mutation does not seem to be responsible for the modification of the biochemical properties of AChE1. This residue is not conserved among species and both resistant and susceptible strains of T. urticae from Japan have a T at position 280. Kwon et al. present evidences that A280T reduce OP sensitivity of AChE and contribute to resistance. The amino acid substitution was modified accordingly in the database
AChE gene duplication results in the proportional overexpression which is necessary for the reduced catalytic activity caused by mutations