Ce. Berkman et al., STEREOSELECTIVE INHIBITION OF HUMAN BUTYRYLCHOLINESTERASE BY PHOSPHONOTHIOLATE ANALOGS OF (-COCAINE AND (-)-COCAINE()), Biochemical pharmacology, 54(11), 1997, pp. 1261-1266
The hydrolysis of cocaine (benzoylecgonine methyl ester) to ecgonine m
ethyl ester by human butyrylcholinesterase (BuChE; EC 3.1.1.8) has bee
n shown previously to constitute an important means to detoxicate this
material to pharmacologically inactive metabolites. The naturally occ
urring (-)-cocaine is hydrolyzed to ecgonine methyl ester approximatel
y 2000 times slower than the unnatural (+)-cocaine isomer. In good agr
eement with previous studies, (-)-cocaine bound to human BuChE with re
latively good affinity and competitively inhibited the hydrolysis of t
he spectrophotometric substrate butyrylthiocholine with a K-i value of
8.0 mu M. Similarly, (+)-cocaine also showed relatively high affinity
for the human BuChE and competitively inhibited butyrylthiocholine hy
drolysis with a K-i value of 5.4 mu M. The phosphonothiolates correspo
nding to the transition state analogs for both (-)- and (+)-cocaine hy
drolysis were synthesized and tested as inhibitors of human BuChE-cata
lyzed hydrolysis of butyrylthiocholine. The phosphonothiolate correspo
nding to the transition state for (-)-cocaine hydrolysis was a competi
tive inhibitor with a K-i value of 55.8 mu M The phosphonothiolate cor
responding to the transition state for (+)-cocaine hydrolysis gave a K
-i value of 25.9 mu M, but, in addition, it also showed irreversible i
nhibition with a k(i) of inactivation of 68.8 min(-1) M-1. It is likel
y that the mechanism-based inhibitor described herein may find use as
a mechanistic probe of butyrylcholinesterase action and also possibly
aid in the purification of this class of esterases. (C) 1997 Elsevier
Science Inc.