Properties of choline acetyltransferase from the bulb miteRhizoglyphus echinopus (Acari: Acaridae)

In the presence of exogenous acetyl coenzyme A¹⁴-C and choline, the 20 000 g supernatant fraction of whole bulb-mite homogenates synthesized a radioactive product that chromatographed with authentic acetylcholine (ACh). ApparentK_m values were 0.12 and 1.14 mM for acetyl coenzyme A and choline, respectively, and the average rate of ACh synthesis was 2.06 mol h^–1 g^–1 equivalent of mite tissue (wet weight). Choline acetyltransferase (ChAT) activity was inhibited by 5,5-dithiobis(2-nitrobenzoic acid), suggesting the presence of functionally important sulfhydryl groups. However, ChAT activity was not inhibited by 27 acaricides from several different chemical classes, except for the thiazolidine flubenzimine which gave a pI₅₀ of 3.5 mol l^–1.Contribution from the Missouri Agricultural Experiment Station, Columbia, Missouri, Journal Series No. 11 157.