LcαE7 is an insect carboxylesterase from Australian sheep blowfly Lucilia cuprina that plays an important role in the detoxification of organophosphates and lipid metabolism. Wild-type LcαE7 is known to exist in an equilibrium between monomer, dimer and a high molecular weight species that is a tetramer. Evolution was used to increase the thermal stability of LcαE7 allowing for over expression for structure determination, leading to the variant, LcαE7-4. A consequence of the evolution towards increased thermostability was a shift in the equilibrium of the oligomeric structures towards the high molecular weight species. Kinetic studies of a mixture of LcαE7-4 showed there was biphasic decay suggesting multiple species with differences of stability. The monomer and tetramer displayed differences in substrate inhibition which suggests conformational differences between the two species. The LcαE7-4 tetramer is less active than the wild type monomer but the trade-off for activity seems to be able to tolerate heat stress.