engleski

Coumarin derivative - inhibitior of acetylcholinesterase and butyrylcholinesterase

It was shown earlier that the coumarin derivative 3-chloro-7-hydroxy-4-methylcoumarin (CHMC) is an allosteric inhibitor of acetylcholinesterase (AChE; EC 3.1.1.7) and butyrylcholinesterase (BChE; 3.1.1.8). Binding of the CHMC to recombinant mouse w t. AChE and BChE, to peripheral site-directed AChE mutants and to human serum BChE variants has now been studied. Enzyme/inhibitor dissociation constants for the catalytic and peripheral sites were evaluated from the apparent dissociation constants as a function of the substrate concentration. The competition between substrate and CHMC displayed two binding sites on AChE mutants: Y72N, Y124Q, W286A and W286R, and the atypical and fluoride-resistant BChE variants. CHMC displayed binding only to the catalytic site (Ka = 0.1 mM) of Y72N/Y124Q/4V286A mutant and only to the peripheral site of AChE wt. (Ki = 0.03 mM) and usual BChE (Ki = 0.2 mM). CHMC had the lowest affinity for the Y72N/Y124Q/W286A mutant and for usual BChE. Molecular modelling of CHMC binding to mouse wt. AChE, using a simulated annealing protocol, revealed two nearly equienergetic clusters of stable CHMC conformations: one in the AChE active center stacked to W86, and the other one at the AChE peripheral site stacked between W286 and Y341. The existence of two binding sites for CHMC on mouse AChE are consistent with results of in vitro inhibition experiments.

coumarin derivative; acetylcholinesterase and site directed mutants; butyrylcholinesterase; human serum butyrylcholinesterase variants; molecular modelling of cholinesterase inhibition

nije evidentirano