Kinetics of human serum butyrylcholinesterase and its inhibition by a novel experimental Alzheimer therapeutic, bisnorcymserine

Article type: Research Article

Authors: Kamal, Mohammad A.^{a; #} | Klein, Peter^b | Yu, Qian-sheng^c | Tweedie, David^c | Li, Yazhou^c | Holloway, Harold W.^c | Greig, Nigel H.^{c; *}

Affiliations: [a] Enzymoics, 7 Peterlee Pl., Hebersham, NSW 2770, Australia | [b] TAFE, Ultimo, NSW 2007, Australia | [c] Drug Design & Development Section, Laboratory of Neurosciences, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA

Correspondence: [*] Corresponding author: Nigel H. Greig, Drug Design & Development Section, Gerontology Research Center, Room 2C13, 5600 Nathan Shock Dr., Baltimore, MD 21224, USA. Tel.: +1 410 558 8278; Fax: +1 410 558 8695; E-mail: Greign@grc.nia.nih.gov.

Note: [#] Information Regarding Enzyme Kinetics: Mohammad A. Kamal, Fax: +1 501 636 8847; E-mail: makamal@optusnet.com.au.

Abstract: An explosion in the incidence of neurodegenerative diseases, particularly Alzheimer's disease (AD), is predicted in coming decades. Hence, the need to devise and assess new treatment strategies has never been more acute. AD, although an irreversible and progressive disorder, is currently treated with palliative, symptomatic therapy: primarily with acetylcholinesterase (AChE) inhibitors to amplify remaining cholinergic activity. New agents that, additionally, affect disease progression are sorely needed. Inhibition of brain butyrylcholinesterase (BuChE) represents a new drug target for AD treatment. Therefore, hand-in-hand with the development of selective ligands to inhibit BuChE in brain, it is fundamental to optimize assay conditions for kinetic studies of human BuChE. Kinetic analysis of serum BuChE, which is structurally similar to brain enzyme, was performed at dual substrate (butyrylthiocholine iodide) concentration ranges: 3–80 μM (low) and 25–800 μM (optimal) by use of the Ellman technique. Interaction of BuChE with a novel experimental AD therapeutic, bisnorcymserine (BNC; 0.06–2.0 nM) was also studied ex vivo. The IC50 and other key kinetic constants were determined for human serum BuChE inhibition by BNC, which proved to be a highly potent inhibitor in comparison to its structural analogue, cymserine. BNC may, additionally, lower the amyloid plaque-associated protein, amyloid-β peptide. In synopsis, the characterization of the kinetic parameters of BuChE and BNC, described herein, is both aiding in the design of novel agents and optimizing their translation toward clinical use.

Keywords: Alzheimer's disease, bisnorcymserine, butyrylcholinesterase, acetylcholinesterase, anticholinesterases, enzyme kinetics, phenserine, physostigmine, cholinergic

DOI: 10.3233/JAD-2006-10108

Journal: Journal of Alzheimer's Disease, vol. 10, no. 1, pp. 43-51, 2006