EVALUATION OF THE NATURE OF CAMEL RETINAL ACETYLCHOLINESTERASE - INHIBITION BY HEXAMETHONIUM

Acetylcholinesterase (AChE, EC 3.1.1.7) has been demonstrated in retin as of several species, however, the nature of the interaction of AChE with specific inhibitors are very limited in the literature and the mo de of inhibition of camel retinal AChE by hexamethonium has been studi ed. Hexamethonium reversibly inhibited AChE in a concentration depende nt manner, the IC50 value being c. 2.52 mM. The K-m for the hydrolysis of acetylthiocholine iodide was found to be 0.087 mM and the V-max wa s 0.63 mu mol/min/mg protein. Dixon, as well as Lineweaver-Burk, plots and their secondary replots indicated that the nature of the inhibiti on is of the hyperbolic (partial) mixed type, which is considered to b e a partial competitive and non-competitive mixture. The values of K-i (slope) and K-I(intercept) from a Lineweaver-Burk plot were estimated as 0.30 mM and 0.17 mM, respectively, while K-i from a Dixon plot was estimated as 0.725 mM. The K-i was greater than K-I indicating that he xamethonium has a greater affinity of binding for the active site than the peripheral site of the camel retina AChE.