Author/Editor     Fekonja, Ota; Zorec-Karlovšek, Majda; El Kharbili, Manale; Fournier, Didier; Stojan, Jure
Title     Inhibition and protection of cholinesterases by methanol and ethanol
Type     članek
Source     J Enzyme Inhib Med Chem
Vol. and No.     Letnik 22, št. 4
Publication year     2007
Volume     str. 407-15
ISSN     1475-6366
Language     eng
Abstract     The cholinesterases have been investigated in terms of the effects of methanol and ethanol on substrate and carbamate turnover; and on their phosphorylation. It was found: 1) that at low substrate concentrations the two alcohols inhibit all three tested cholinesterases and that the optimum activities are shifted towards higher substrate concentrations, but with a weak effect on horse butyrylcholinesterase; 2) that methanol slows down carbamoylation by eserine and does not influence decarbamoylation of vertebrate and insect acetylcholinesterase and 3) that ethanol decreases the rate of phosphorylation of vertebrate acetylcholinesterase by DFP. Our results are in line with the so-called 'approach-and-exit' hypothesis. By hindering the approach of substrate and the exit of products, methanol and ethanol decrease cholinesterase activity at low substrate concentrations and allow for the substrate inhibition only at higher substrate concentrations. Both effects appears to be a consequence of the lower ability of substrate to substitute alcohol rather than water. It also seems that during substrate turnover in the presence of alcohol the transacetylation is negligible.
Descriptors     ACETYLCHOLINESTERASE
BUTYRYLCHOLINESTERASE
ENZYME INHIBITORS
KINETICS
ALCOHOL, ETHYL
ALCOHOL, METHYL
ACETYLTHIOCHOLINE
BUTYRYLTHIOCHOLINE
ISOFLUROPHATE
HYDROLYSIS
PHOSPHORYLATION
PHYSOSTIGMINE