HUMAN ERYTHROCYTE BUT NOT BRAIN ACETYLCHOLINESTERASE HYDROLYSES HEROIN TO MORPHINE

Authors

  • Asher Y Salmon,

    1. 11Department of Biological Chemistry, Institute of Life Sciences, Hebrew University of Jerusalem, Givat Ram and 22Analytical Chemistry Laboratory, Division of Identification and Forensic Science, Israel Police, Jerusalem, Israel
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  • 1 Zafrir Goren,

    1. 11Department of Biological Chemistry, Institute of Life Sciences, Hebrew University of Jerusalem, Givat Ram and 22Analytical Chemistry Laboratory, Division of Identification and Forensic Science, Israel Police, Jerusalem, Israel
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  • 2 Yaniv Avissar,

    1. 11Department of Biological Chemistry, Institute of Life Sciences, Hebrew University of Jerusalem, Givat Ram and 22Analytical Chemistry Laboratory, Division of Identification and Forensic Science, Israel Police, Jerusalem, Israel
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  • and 2 Hermona Soreq 1

    1. 11Department of Biological Chemistry, Institute of Life Sciences, Hebrew University of Jerusalem, Givat Ram and 22Analytical Chemistry Laboratory, Division of Identification and Forensic Science, Israel Police, Jerusalem, Israel
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Dr Hermona Soreq Department of Biological Chemistry, Institute of Life Sciences, Hebrew University of Jerusalem, Givat Ram, Jerusalem 91904, Israel. Email: <soreq@shum.huji.ac.il>

Abstract

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.

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