Mode of inhibition of bovine retinal Acetylcholinesterase by Gallamine triethiodide in vitro
2000
Kamal, M.A. | Al-Jafari, A.A. (King Saud Univ., Riyadh (Saudi Arabia). Dept. of Biochemistry)
The current study addresses the kinetic analyses of the interaction of gallamine triethiodide with bovine retinal acetylcholinesterase (AChE, EC 3.1.1.7). The Michaelis-Menten constant (Ks) of the control for the hydrolysis of acetylthiocholine iodide (ASCh) by AChE was 0.072 mM and it was increased by 32.9 - 50.3 % for the gallamine (0.05 - 1.5 mM) treated enzyme. The Vmax, was 0.82 micro-mol/min/mg protein for the control system; it was decreased by 8.4 - 60.5 % in the gallamine treated systems. The Lineweaver-Burk plot, Dixon plot and their secondary replots indicated that the nature of the inhibition was that of neither a linear nor a hyperbolic, conventional mixed type of inhibition system. We refer to this new mode of inhibition as a "non- linear-non- hyperbolic" mixed type inhibition, which is composed of a mixture of competitive and noncompetitive inhibition. The values for Ki and K1 were estimated to be 0.69 and 1.096 mM, respectively. These findings in the current study indirectly approach towards understanding of the binding sites of the bovine retinal AChE in the light of comparison with reported data for Torpedo, chicken and camel retinal AChE.
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