TY - JOUR
T1 - Human erythrocyte but not brain acetylcholinesterase hydrolyses heroin to morphine
AU - Salmon, Asher Y.
AU - Goren, Zafrir
AU - Avissar, Yaniv
AU - Soreq, Hermona
PY - 1999
Y1 - 1999
N2 - 1. In human blood, heroin is rapidly hydrolysed by sequential deacylation of two ester bonds to yield first 6-monoacetylmorphine (6-MAM), then morphine. 2. Serum butyrylcholinesterase (BuChE) hydrolyses heroin to 6- MAM with a catalytic efficiency of 4.5/min per μmol/L, but does not proceed to produce morphine. 3. In vitro, human erythrocyte acetylcholinesterase (ACHE) hydrolyses heroin to 6-MAM, with a catalytic efficiency of 0.5/min per μmol/L under first-order kinetics. Moreover, erythrocyte ACHE, but not BuChE is capable of further hydrolysing 6-MAM to morphine, albeit at a considerably slower rate. 4. Both hydrolysis steps by erythrocyte AChE were totally blocked by the selective AChE inhibitor BW284c51 but were not blocked by the BuChE-specific inhibitor, iso-OMPA (tetraisopropylpyrophosphoramide). 5. The brain synaptic form of AChE, which differs from the erythrocyte enzyme in its C-terminus, was incapable of hydrolysing heroin. 6. Heroin suppressed substrate hydrolysis by antibody-immobilized erythrocyte but not by brain ACHE. 7. These findings reveal a new metabolic role for erythrocyte AChE, the biological function of which is as yet unexplained, and demonstrate distinct biochemical properties for the two AChE variants, which were previously considered catalytically indistinguishable.
AB - 1. In human blood, heroin is rapidly hydrolysed by sequential deacylation of two ester bonds to yield first 6-monoacetylmorphine (6-MAM), then morphine. 2. Serum butyrylcholinesterase (BuChE) hydrolyses heroin to 6- MAM with a catalytic efficiency of 4.5/min per μmol/L, but does not proceed to produce morphine. 3. In vitro, human erythrocyte acetylcholinesterase (ACHE) hydrolyses heroin to 6-MAM, with a catalytic efficiency of 0.5/min per μmol/L under first-order kinetics. Moreover, erythrocyte ACHE, but not BuChE is capable of further hydrolysing 6-MAM to morphine, albeit at a considerably slower rate. 4. Both hydrolysis steps by erythrocyte AChE were totally blocked by the selective AChE inhibitor BW284c51 but were not blocked by the BuChE-specific inhibitor, iso-OMPA (tetraisopropylpyrophosphoramide). 5. The brain synaptic form of AChE, which differs from the erythrocyte enzyme in its C-terminus, was incapable of hydrolysing heroin. 6. Heroin suppressed substrate hydrolysis by antibody-immobilized erythrocyte but not by brain ACHE. 7. These findings reveal a new metabolic role for erythrocyte AChE, the biological function of which is as yet unexplained, and demonstrate distinct biochemical properties for the two AChE variants, which were previously considered catalytically indistinguishable.
KW - 6- monoacetylmorphine
KW - Acetylcholinesterase
KW - Brain
KW - Butyrylcholinesterase
KW - Erythrocytes
KW - Heroin
KW - Morphine
KW - Opiates
UR - http://www.scopus.com/inward/record.url?scp=0032770793&partnerID=8YFLogxK
U2 - 10.1046/j.1440-1681.1999.03090.x
DO - 10.1046/j.1440-1681.1999.03090.x
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C2 - 10474772
AN - SCOPUS:0032770793
SN - 0305-1870
VL - 26
SP - 596
EP - 600
JO - Clinical and Experimental Pharmacology and Physiology
JF - Clinical and Experimental Pharmacology and Physiology
IS - 8
ER -