Human Erythrocyte

7/29/2019 Human Erythrocyte

1/5

SUMMARY

1. In human blood, heroin is rapidly hydrolysed by sequential

deacylation of two ester bonds to yield first 6-monoacetylmor-

phine (6-MAM), then morphine.

2. Serum butyrylcholinesterase (BuChE) hydrolyses herointo 6-MAM with a catalytic efficiency of 4.5/min permol/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 mol/L under first-order kinetics. Moreover,

erythrocyte AChE, but not BuChE is capable of furtherhydroly-

sing 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 ofhydrolysing 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.

Key words: acetylcholinesterase, brain, butyrylcholinesterase,

erythrocytes, heroin, 6-monoacetylmorphine, morphine, opiates.

INTRODUCTION

Heroin (3,6-diacetylmorphine) is a worldwide leading cause of

morbidity and mortality due to drug abuse. In certain countries,

heroin is legally used for treating chronic pain and for other medical

purposes.1

In the human bloodstream, heroin is rapidly hydrolysedto 6-monoacetylmorphine (6-MAM) and then into morphine.2 The

serum enzyme butyrylcholinesterase (BuChE, acylcholine acylhy-

drolase, EC 3.1.1.8) has been shown to perform the first but not the

second step in this process.3,4 Moreover, physiological studies have

demonstrated that heroin degradation occurs primarily in the

micro-environment of erythrocytes, where BuChE is absent, but not

in the serum.5,6 Two major esterases and a few non-specific

esterases are present in human erythrocytes. These are arylesterase

(EC.3.1.1.2) and acetylcholinesterase (AChE, acetylcholine acetyl-

hydrolase, EC.3.1.1.7). Lockridge et al. demonstrated that serum

BuChE, but not erythrocyte arylesterase, is capable of hydrolysing

heroin.3 This left two questions unanswered: first, can erythrocyte

AChE hydrolyse heroin? and second, can it degrade it completelyto morphine? Acetylcholinesterase, whose main catalytic activity

is to hydrolyse the neurotransmitter acetylcholine, appears in three

C-terminally distinct isoforms, derived from alternatively spliced

AChE mRNA species.7 Therefore, nervous system AChE differs

from red blood cell AChE in its C-terminal peptide. Because both

6-MAM and morphine, but not heroin, are physiologically active

in the mammalian brain,8 another issue arises: whether the brain

and red blood cell variants of AChE differ in their capacity to

hydrolyse heroin and/or 6-MAM. To address these issues, we com-

bined the use of highly purified AChE isoforms with high-pressure

liquid chromatography (HPLC) for testing heroin degradation

kinetics by the various isoforms of human AChE.

MATERIALS AND METHODS

Human AChE from erythrocytes (Sigma type XIII); human serum BuChE,

human recombinant AChE (brain form), chromatographic standards (heroin

hydrochloride, morphine sulphate, 6-MAM), 1,5-bis 4-allyldimethylam-

moniumphenyl pentan-3-one dibromide, (BW284c51), tetraisopropylpyro-

phosphoramide (iso-OMPA), acetylthiocholine (ATCh), butyrylthiocholine

(BTCh) and other basic chemicals were all purchased from Sigma Chemical

Co. (St Louis, MO, USA). Morphine-HCl and codeine sulphate were pur-

chased from Teva Co. (Kfar-Saba, Israel). High-performance liquid chroma-

tography reagents were purchased from Cavlo Ebra (Paris, France).

Monoclonal mouse antihuman BuChE (no. 534) and antihuman AChE

(no. 1011)7 were gratefully received from Dr B. Norgaard-Pedersen

BRIEF REVIEW

HUMAN ERYTHROCYTE BUT NOT BRAINACETYLCHOLINESTERASE HYDROLYSES HEROIN TO MORPHINE

Asher Y Salmon,1 Zafrir Goren,2 Yaniv Avissar2 and Hermona Soreq1

1Department of Biological Chemistry, Institute of Life Sciences, Hebrew University of Jerusalem,

Givat Ram and2Analytical Chemistry Laboratory, Division of Identification and Forensic Science,

Israel Police, Jerusalem, Israel

Correspondence: Dr Hermona Soreq, Department of Biological Chemistry,

Institute of Life Sciences, Hebrew University of Jerusalem, Givat Ram,

Jerusalem 91904, Israel. Email:

Presented as an invited lecture at the Annual Meeting of the Australian

Physiological and Pharmacological Society (APPS), Brisbane, September

October 1998.

Received 5 January 1999; accepted 14 April 1999.

Clinical and Experimental Pharmacology and Physiology (1999) 26, 596600


2/5

Heroin hydrolysis by human acetylcholinesterase 597

(Copenhagen, Denmark). Heroin HCl, 6-monoacetylmorphine (6-MAM) and

3-monoacetylmorphine (3-MAM) were purified and standardized prior to

experimentation as previously described.

Opiates hydrolysis by ChEs

Opiates (85mol/L) were incubated under agitation with 0.5 units per mL

cholinesterase, in sodium phosphate buffer (0.1 mol/L, pH 7.4) at 37C. One

unit of enzyme will hydrolyse 1mol per min of BTCh or ATCh at pH 8.0

at 37C. Hydrolysis was terminated by removing 400 L aliquots from thereaction mixture at timed intervals, adding 17 L of 1 mmol/L H2SO4 and

200L methanol and placing the mixture on ice, where the low temperature

and pH suppressed both enzymatic and spontaneous hydrolysis.9

High-performance liquid chromatography analysis

A total of 10 nmol/L acetyl-codeine was added to each stopped reaction

mixture as a high-powered liquid chromatography (HPLC) internal standard.

The resultant mixtures were filtered through a 0.45 m membrane and

injected into a Waters 717 auto-sampler (Milford, MA, USA) at 4C.

Duplicates of 10L samples were deposited onto MerckTM RP (Darmstadt,

Germany) Select B-125 4 (5m particle size) HPLC columns at 27C.

The mobile phase gradient elution contained 2 mmol/L sulphuric acid in

water, in acetonitrile and in methanol with a flow rate of 1.8mL/min.

Chromatograms were recorded at 230 nm with a Waters 996 photodiode

array detector. Absorption spectra for each peak were recorded between 200

and 350 nm (1.2 nm resolution). Duplicate measurements of peak areas were

processed by Millenium 2.1 data analysis (Waters). Michaelis-Menten con-

stant (Km) values for heroin hydrolysis by ChEs was derived from double

reciprocal Lineweaver-Burk plots over a substrate range of 324000

mol/L.

Immobilization of cholinesterases

Mouse antihuman serum BuChE or monoclonal antihuman AChE anti-

bodies10 were absorbed to microtitre plates (Nunc, Roskilde, Denmark) at

0.5 g/mL in 0.1mol/L carbonate buffer, pH 9.6, for at least 4h at room

temperature. Plates were then washed three times in phosphate-buffered

saline (PBS)-T buffer (144 mmol/LNaCl, 20 mmol/LNa phosphate, pH7.4,

0.05% Tween-20). Free binding sites on the surface of the microtitre plate

wells were blocked with PBS-T for 1 h at 37C. Cholinesterases were then

added at a concentration of 100 mIU/mL in PBS-T for at least 3 h at room

temperature with agitation. Plates were washed three times with PBS-T

before use.

Inhibition of cholinesterase activity by heroin

Heroin, 6-MAM, morphine and codeine at 650mol/L in 180L of Ellmans

solution11 were added to antibody-immobilized enzymes12 for 5 min at room

temperature, followed by three washes with PBS-T to remove free opiates.

Rates of ATCh (1 mmol/L) or BTCh (10 mmol/L) hydrolysis were determined

spectrophotometrically.11,12 Inhibition constant (Ki) values were determined

by measuring cholinesterase activity in a solution containing 305000

mol/L concentrations of heroin, 6-MAM or morphine as inhibitors andATCh or BTCh as substrates. Ki values were calculated as described previ-

ously, Ki IC50/(1 S/Km),13 following inhibition of substrate hydrolysis

by 305000mol/L opiate over a substrate range of 0.110 mmol/L.

RESULTS

Both isolated human serum BuChE and erythrocyte AChE were

capable of hydrolysing heroin to 6-MAM, although at different rates

(Fig. 1). Human BuChE (0.5IU) hydrolysed the physiologically

relevant initial amount of 85 nmol heroin in 1mL (36 g) with a half-

life (1/2) of 3.5 min, close to the reported in vivo enzyme/

substrate ratio and 1/2 value of heroin in blood of 25 min.6,14,15 In

the present study, BuChE did not further hydrolyse 6-MAM to

morphine, in agreement with the findings of Lockridge et al.,3 but

unlike the findings of Kamendulis et al.4 The BuChE Km for heroin

was 110 mol/L with catalytic constant (kcat) of 540/min (Table

1). Under similar conditions erythrocyte AChE C-terminated with

the peptide encoded by exon 5,7 hydrolysed 85 nmol heroin in 1 mL

to 6-MAM with the longer 1/2 of 25 min. Erythrocyte AChE further

displayed higher Km (620 mol/L) and a lower kcat (351/min) val-

ues for heroin hydrolysis than those of BuChE, reflecting weaker

affinity and/or catalytic efficiency than those of BuChE. This was

in line with the nine-fold difference in the catalytic efficiencies of

BuChE and erythrocyte AChE in hydrolysing heroin (4.5 and

0.5/min per mol/L, respectively). However, unlike BuChE, AChE-

E5 proceeded to hydrolyse 6-MAM to morphine, although at the

low rate of 0.1nmol/min (Fig. 1). Heroin hydrolysis by AChE-E5

was not affected by 10mol/L of the selective BuChE inhibitor iso-

OMPA (data not shown). In contrast, no hydrolysis was observed

in the presence of AChE-E5 and 10mol/L of the selective AChE

inhibitor BW284c51, except for the expected rate of spontaneous

hydrolysis (0.07 nmol/min). This confirmed that it was red blood

cell AChE that hydrolysed heroin, excluding the possibility of con-

taminating enzymes.

Interestingly, no hydrolysis was detected when 6-MAM was

added to erythrocyte AChE as a substrate, demonstrating that AChE-

E5 could degrade 6-MAM only when produced from heroin within

its active site. In contrast, the non-natural metabolite 3-MAM was

efficiently hydrolysed to morphine, both by BuChE and AChE-E5

(data not shown). Recombinant AChE, consisting of the synaptic

AChE form, abundant in the human brain and C-terminated by the

exon 6-encoded peptide, did not significantly hydrolyse heroin, 6-

MAM or 3-MAM (Fig.1 and data not shown).

Because both heroin and 6-MAM are much poorer cholinesterase

substrates than the acylthiocholines, they could also be considered

as inhibitors of thiocholine ester hydrolysis. Ki determinations for

heroin and 6-MAM revealed a decreasing order of affinities for their

interactions with BuChE, AChE-E5 and AChE-E6 (Table 1).

Consistent with the observed relative rates of catalysis, the Ki values

of BuChE and AChE-E5 for morphine were approximately 10-fold

higher, reflecting considerably weaker affinities than those for heroin

and 6-MAM.

To further explore the interaction(s) between various

cholinesterase variants and opiate derivatives, we added heroin,

6-MAM, morphine or codeine (as a control) to solid phase-

conjugated enzymes. Following 5min incubation with 650 mol/L

of the noted agents and washing to remove unbound drug, we tested

the residual capacity of these enzymes to hydrolyse ATCh or BTCh

using a spectrophotometric assay adapted for use with microtitre

plates.16 When tested within 5 min of drug removal, codeine did not

affect substrate hydrolysis by BuChE, AChE-E5 or AChE-E6. In

contrast, heroin enhanced the activity of BuChE by 25% and inhib-

ited the activity of AChE-E5 by 28%. There was almost no effect

of heroin on substrate hydrolysis by AChE-E6, consistent with its

inability to hydrolyse heroin. 6-Monoacetylmorphine inhibited the

activity of BuChE, AChE-E5 and AChE-E6 by 30%, 25% and 22%,

respectively (Table 1). All three enzymes displayed full activity

within 60min of drug removal.

DISCUSSION

Using purified native and recombinant variants of human

cholinesterases,17 we have demonstrated that erythrocyte, but not


3/5

598 AY Salmon et al.

the brain, AChE can hydrolyse heroin to 6-MAM at a physiologically

relevant rate not much lower than that of serum BuChE; that erythro-

cyte AChE, but not serum BuChE, can further degrade 6-MAM to

morphine and that both heroin and 6-MAM affect the catalytic

properties of erythrocyte AChE and serum BuChE. These findings

suggest that erythrocyte AChE hydrolyses heroin in human blood

Fig. 1. Heroin hydrolysis. (a) In vivo

metabolism. The structures of heroin, 6-

monoacetylmorphine (6-MAM) and mor-

phine are shown. Sites of enzyme hydrolysis

are marked by arrows. Intravenous injection

of heroin leads to rapid hydrolysis of the esterbond at position 3, yielding 6-MAM (1/225 min),6 followed by a slower rate

hydrolysis of the ester bound at position 6,

yielding morphine (1/230 min).2 (b) In

vitro hydrolysis by cholinesterase variants.

Cholinesterase variants encoded by the noted

exons (E) differ in their entire sequence

(between butyrylcholinesterase (BuChE) and

acetylcholinesterase (AChE)) or in their C-

terminal peptides, encoded by E5 or E6 (for

red blood cells (RBC) and brain AChE,

respectively). Enzymes were incubated with

85mol/L heroin and levels of the noted opi-

ate derivatives (, heroin; , 6-MAM; ,

morphine). Presented are residual fractions of

heroin and accumulation of 6-MAM andmorphine as a function of time (in different

time scales for each enzyme). Calculated t2values were 3.5 min for heroin hydrolysis by

serum BuChE (left), 25 min for heroin

hydrolysis by erythrocyte AChE-E5 (RBC,

centre) and no hydrolysis for synaptic AChE-

E6 (right). Note morphine production only by

AChE-E5 and the slow spontaneous hydrol-

ysis of heroin into 6-MAM during the long-

term incubation with AChE-E6, which

correlates well with incubation in the absence

of enzyme (up to 0.07 nmol/min). One out of

two experiments with duplicates differed in

less than 8%.

Table 1. Effects of heroin and its derivatives on the catalytic activities of cholinesterase variants

Enzyme variants

Serum BuChE Erythrocyte AChE-E5 Brain AChE-E6

Heroin

Km, mol/L* 110 620 NS

kcat/min 540 351 NS

Catalytic efficiency/min per mol/L 4.5 0.55 NS

Ki (mol/L) 442 765 1533

% Remaining immobilized enzyme activity 1254 727 964

6-MAM

Ki (mol/L) 304 656 1302

% Remaining immobilized enzyme activity 704 752 781

Morphine

Ki (mol/L)* 63320 52612 5119

% Remaining immobilized enzyme activity 1004.1 990.5 980.5

Codeine No detectable effects

*Km values were derived from double reciprocal Lineweaver-Burk plots over a heroin concentration range of 324000 mol/L.

Kcat values were basedon observed Vmax values (for heroin) divided by the number of enzyme active sites as determined by substrate hydrolysis assays (as described in Materials

and Methods) and using turnover numbers reported for human AChE (16) and BuChE (12). Ki values for inhibition of substrate hydrolysis by 305000mol/L

opiate over a substrate range of 0.110 mmol/L. One out of three reproducible experiments with triplicate measurements. Per cent inhibition of substrate

(ATCh or BTCh) hydrolysis capacity as measured on antibody-immobilized enzyme following 5 min incubation with 100L of 650mol/Ldrug and subsequent

washes. One out of three reproducible experiments with triplicate measurements. Activity of antibody-immobilized enzyme incubated without drug served

as control and referred to as 100% activity (the activity of the different enzymes was almost the same (>95%) as the initial activity before treatment).

NS, non-significant; BuChE, butyrylcholinesterase; AChE, acetylcholinesterase; BTCh, butyrylthiocholine; ATCh, acetylthiocholine.


4/5

Heroin hydrolysis by human acetylcholinesterase 599

and demonstrate the first biochemical distinction between the

previously indistinguishable AChE variants12 expressed in the brain

and haematopoietic cells.

While BuChE is well known for its wide range of substrates,

AChEs specificity is much more limited, which is considered to

contribute towards the high rate of ACh hydrolysis.18 In addition to

their active site, both enzymes possess peripheral binding sites for

substrates and inhibitors.12 The difference between the erythrocyte

and brain AChE variants is in their distinct C-terminal domains,7

and ample biochemical evidence demonstrates that these C-terminal

domains are only loosely associated with the globular enzyme core

unit.18,19 This indicates that the alignment of the C-terminus along

the protein core may affect heroin binding, perhaps by physical

masking of a peripheral domain in only one of the two variants.

The fact that 6-MAM cannot serve as a substrate but can serve

as an inhibitor for AChE-E5 suggests that in order to be hydrolysed

6-MAM must be correctly positioned within the active site of AChE.

The efficient hydrolysis of 3-MAM indicates that the 3-acetyl but

not the 6-acetyl group is required for proper access of the molecule

6-MAM into the active site groove. In addition, the distinct inter-

actions of the various opiate derivatives with cholinesterase variants

may reflect binding to the well-recognized peripheral site.20 Thus,

the 3-acetyl group of the drug enables interaction with the enzyme

through its peripheral site. This latter hypothesis is strengthened by

the apparent similarity between the heroin-induced enhancement of

BTCh hydrolysis by immobilized BuChE and the phenomenon of

substrate activation previously reported for BuChE.2123 The inhi-

bition of AChE-E5 by heroin is similarly parallel to the substrate

inhibition characteristic of this enzyme.24 Both BuChE substrate acti-

vation and AChE substrate inhibition were attributed in these and

other studies to a peripheral binding site(s).2124 The fact that heroin

does not affect AChE-E6 hydrolysis, leads us to tentatively attribute

the heroinAChE peripheral interaction to a site masked by the

E6-derived C-terminus.

In spite of the better catalytic profile of BuChE to hydrolyse

heroin, most of the drug hydrolysis in vivo occurs in the erythro-

cyte fraction of human blood.5,6 Since heroin is a highly lypophilic

molecule with a tendency to concentrate on cellular membranes, the

concentration of heroin at the micro-environment of the erythrocyte

membrane may reach much higher values than in the plasma. This

would assist erythrocytic AChE to hydrolyse most of the adminis-

tered heroin. Moreover, we now demonstrate that the second step

of hydrolysis of 6-MAM into morphine can also be carried in this

micro-environment. Red blood cells can therefore serve as efficient

carriers of heroin and 6-MAM from the circulation towards the

bloodbrain barrier, where these compounds penetrate into the brain

to create the rapid onset of heroin effects. Within both the blood

and the brain, the inhibition of BuChE catalysis by 6-MAM supports

the notion of an inhibitory loop whereby 6-MAM production

suppresses BuChEs capacity to hydrolyse heroin.3 In contrast,

6-MAM affects AChE much less and cannot in its free state serve

as a substrate for either AChE variant. Therefore, penetrance of

heroin or 6-MAM into the brain would protect them from the rapid

degradation taking place in the circulation, consistent with previous

in vivo reports.6 The distinct opiate hydrolysing capacities of the

brain and erythrocyte AChE therefore shed new light on heroin

metabolism in humans.

ACKNOWLEDGEMENTS

We would like to thank Dr B Norgaard-Pedersen, Copenhagen, for

anti-AChE and BuChE antibodies. This research was supported by

a grant to HS from the Israel Science Fund.

REFERENCES

1. Inturrisi CE, Max MB, Foley KM, Schultz M, Shin S-U, Houde RW.

The pharmacokinetics of heroin in patients with chronic pain.New Engl.

J. Med. 1984; 310: 121317.

2. Boerner V, Abbot S, Roe RL. The metabolism of morphine and heroin

in man.Drug Metab. Rev. 1975; 4: 3973.

3. Lockridge O, Mattershaw-Jackson N, Eckerson HW, LaDu BN.

Hydrolysis of diacetylmorphine (heroin) by human serum

cholinesterase.J. Pharmacol. Exp. Ther. 1980; 215: 18.

4. Kamendulis LM, Brezezinski MR, Pindel EV, Bosron WF, Dean RA.

Metabolism of cocaine and heroin is catalyzed by the same human

liver carboxylesterases. J. Pharmacol . Exp. Ther. 1996; 279:

71317.

5. Smith DA, Cole WJ. Identification of an arylesterase as the enzyme

hydrolysing diacetylmorphine (heroin) in human plasma. Biochem.

Pharmacol. 1976; 25: 36770.6. Owen JA, Nakatsu K. Diacetylmorphine (heroin) hydrolases in human

blood. Can. J. Physiol. Pharmacol. 1983; 61: 8705.

7. Ben Aziz-Aloya R, Seidman S, Timberg R, Sternfeld M, Zakut H, Soreq

H. Expression of a human acetylcholinesterase promoter-reporter con-

struct in developing neuromuscular junctions ofXenopus embryos. Proc.

Natl Acad. Sci. USA 1993; 90: 24715.

8. Inturrisi CE, Schultz M, Shin S, Umans JG, Angel C, Simon EJ.

Evidence from opiate binding studies that heroin acts through its meta-

bolites.Life Sci. 1983; 33: 7736.

9. Barrett DA, Dyssegaard AL, Shaw PN. The effect of temperature and

pH on the deacylation of diamorphine in aqueous solution and in human

plasma.J. Pharm. Pharmacol. 1992; 44: 6068.

10. Liao J, Mortensen V, Norgaard-Pedersen B, Koch C, Brodbeck U.

Monoclonal antibodies against brain acetylcholinesterase which recog-

nize the subunits bearing the hydrophobic anchor.Eur. J. Biochem.1993;215: 3340.

11. Ellman GL, Courtney D, Anders VJr, Featherstone RM. A new and rapid

colorimetric determination of acetylcholinesterase activity. Biochem.

Pharmacol. 1961; 7: 8895.

12. Schwarz M, Loewenstein-Lichtenstein Y, Glick D, Liao J, Norgaard-

Pedersen B, Soreq H. Successive organophosphate inhibition and oxime

reaction reveals distinct responses of recombinant human cholinesterase

variants.Mol. Brain Res. 1995; 31: 10110.

13. Loewenstein-Lichtenstein Y, Schwarz M, Glick D, Soreq H. Genetic

predisposition to adverse consequences of anti-cholinesterases in

atypical BCHE carriers.Nature Med. 1995; 1: 10825.

14. Martin WR, Fraser HF. A comparative study of physiological

and subjective effects of heroin and morphine administered intra-

venously in post-addicts. J. Pharmacol. Exp. Ther. 1961; 133:

38899.15. Nakamura G, Thornton JI, Noguchi TT. Kinetics of heroin deacylation

in aqueous alkaline solution and in human serum and whole blood.

J. Chromatogr. 1975; 110: 819.

16. Neville LF, Gnatt A, Loewenstein Y, Seidman S, Ehrlich G, Soreq H.

Intramolecular relationships in cholinesterases revealed by oocyte

expression of site-directed and natural variants of human BCHE.

EMBO J. 1992; 11: 16419.

17. Soreq H, Ben-Aziz R, Prody CA et al. Molecular cloning and con-

struction of the coding region for human acetylcholinesterase reveals

a GC-rich attenuating structure. Proc. Natl Acad. Sci. USA 1990; 87:

968892.


5/5

600 AY Salmon et al.

18. Sussman JL, Harel M, Frolow F et al. Atomic structure of acetyl-

cholinesterase from Torpedo californica: A prototype acetylcholine bind-

ing protein. Science 1991; 253: 8729.

19. Taylor P, Radic Z. The cholinesterases: From genes to proteins.Ann.

Rev. Pharmacol. Toxicol. 1994; 34: 281320.

20. Shafferman A, Velan B, Ordentlich A et al. Substrate inhibition of acetyl-

cholinesterase: Residues affecting signal transduction from the surface

to the catalytic center.EMBO J. 1992; 11: 36518.

21. Cauet G, Friboulet A, Thomas D. Horse serum butyrylcholinesterase

kinetics: A molecular mechanism based on inhibition studies withdalensylaminoethyltrimethylammonium.Biochem. Cell. Biol.1987; 65:

52935.

22. Eriksson H, Agustinsson KB. A mechanistic model for butyryl-

cholinesterase.Biochim. Biophys. Acta 1979; 567: 16173.

23. Getley SJ. Activities of the enantiomers of cocaine and some related

compounds as substrates and inhibitors of plasma butyrylcholinesterase.

Biochem. Pharmacol. 1991; 41: 124954.

24. Haas R, Adams EW, Rosenberry MA, Rosenberry TL. Substrate-selec-

tive inhibition and peripheral site labeling of acetylcholinesterase by

platinum (terpyridine) chloride. In: Shafferman A, Velan B (eds).

Multidisciplinary Approaches to Cholinesterase Functions. Plenum

Press, New York. 1992; 1319.

Human Erythrocyte

Documents

Transcript of Human Erythrocyte