Inhibition and protection of cholinesterases by methanol and ethanol

Figures & data

Table I.  Concentrations and proportional factors for ethanol.

Percent	density	ethanol[M]	water[M]	wat]/[wat0]
0.0	1.000	0.00	55.55	1.000
2.5	0.996	0.54	54.17	0.975
5.0	0.992	1.08	52.80	0.950
7.5	0.990	1.61	51.43	0.926
10.0	0.987	2.15	50.07	0.901
12.5	0.984	2.67	48.72	0.877
15.0	0.981	3.20	47.38	0.853
17.5	0.979	3.72	46.04	0.829
20.0	0.976	4.24	44.71	0.805

Figure 1 Cholinesterase activities vs. substrate concentrations (pS curves) for electric eel and insect AChE, and horse BChE (as indicated) in the absence and presence of various concentrations of methanol and ethanol (as indicated).

Table II.  Kinetic constants for the cholinesterases in the presence of substrate, methanol and ethanol according to the scheme given in Appendix.

	EeAChE + ATCh		DromeAChE + ATCh		HorseBCHE + BTCh
	Methanol Ethanol		Methanol Ethanol		Methanol Ethanol
Kp [M]	0.0014		0.00017		0.0014
KL	0.0322		4.17		0.26
KLL	3.65		179		134
k2 1/s	17546		53465		3517
k3 1/s	13497		395		667
a	4.15		3.44		3.8
b	0.26		0.05		0.6
Kip [M]	0.38	2.41	0.67	0.41	1.65	0.18
KiL	1.85	0.27	4.48	56.8	1.01	16.6
KiLL	0.67	0.06	4.48	56.8	0.76	13.2
C	1	1	1	1.35	1	1
D	1	1	1	0.23	1	1
E	1	1	1	1	5.28	3.55
F	1.86	0	1.85	10.85	5.28	3.55
G	3.52	3.35	7.27	15.4	2.25	4.0

Figure 2 Time-courses of acetylcholinesterase inhibition by eserine. A. Electric eel AChE. B. Drosophila melanogaster AChE.

Figure 3 Time-courses of electric eel AChE inhibition by 0.1 mM DFP in the absence and presence of 10% ethanol. Inset: semilogarithmic plot.

Figure 4 Gas chromatograms of various mixtures of ethanol, acetylcholine, cholinesterase, ethyl acetate and sulfuric acid: A) the remaining ethanol from the previous run + ethyl acetate (20%); B) sodium acetate (2 mM) + ethanol (20%)+ sulfuric acid (2 mM); C) ethanol (20%)+ acetylcholine (50 mM); D) ethanol (20%)+ acetylcholine (50 mM) + cholineterase (∼1 nM); E) ethanol (20%)+ acetylcholine (50 mM), after a 2-h incubation; F) ethanol (20%)+ acetylcholine (50 mM) + cholineterase (∼1 nM), after a 2-h incubation.