Structural Determinants ofTorpedocalifornicaAcetylcholinesterase Inhibition by the Novel and Orally Active Carbamate Based Anti-Alzheimer Drug Ganstigmine (CHF-2819)

Abstract

Ganstigmine is an orally active, geneserine derived, carbamate-based acetylcholinesterase inhibitor developed for the treatment of Alzheimer's disease. The crystal structure of the ganstigmine conjugate with Torpedo californica acetylcholinesterase (TcAChE) has been determined at 2.40 A resolution, and a detailed structure-based analysis of the in vitro and ex vivo anti-AChE activity by ganstigmine and by new geneserine derivatives is presented. The carbamoyl moiety is covalently bound to the active-site serine, whereas the leaving group geneseroline is not retained in the catalytic pocket. The nitrogen atom of the carbamoyl moiety of ganstigmine is engaged in a key hydrogen-bonding interaction with the active site histidine (His440). This result offers an explanation for the inactivation of the catalytic triad and may account for the long duration of action of ganstigmine in vivo. The 3D structure also provides a structural framework for the design of compounds with improved binding affinity and pharmacological properties.

The Kinetics of Inhibition of Human Acetylcholinesterase and Butyrylcholinesterase by Two Series of Novel Carbamates

“…In rhAChE, larger N-alkyl groups may be accommodated in a region that spans the less crowded entrance to the gorge, thereby providing tighter binding with less steric constraint. This is consistent with the TcAChE crystal structures for mono N-substituted carbamates with a bulky N-substituent (Bartolucci et al, 1999(Bartolucci et al, , 2006.…”

“…Most published analyses of structure-activity relationships of carbamates designed as potential drugs for the treatment of AD are based on measurements of IC 50 (Yu et al, 2001;Sterling et al, 2002;Bolognesi et al, 2004;Luo et al, 2005Luo et al, , 2006Bartolucci et al, 2006). However, this parameter lacks information on the individual rate constants that govern the approach to, and the steady-state level of, enzyme activity and the rate of release of a leaving group designed to exert independent biological activity.…”

“…Despite these unexplained kinetic discrepancies between the two enzymes, the crystal structures of covalent conjugates, formed between TcAChE and bulky N-substituted mono-and dialkyl-carbamates with large leaving groups, provide information on the relative orientation of the covalently bound carbamyl moiety and may assist in the rationalization of results obtained from the kinetics of inhibition of rhAChE by the AI and PE series. While the N-methyl,Nethyl carbamyl adduct of rivastigmine disrupted the catalytic triad (Bar-On et al, 2002), the bulky mono-N-alkyl carbamates of (N-cis-2,6-dimethylmorpholino-octyl chain (Bartolucci et al, 1999) and the (N-2Ј-ethyl phenyl) moiety of ganstigmine (Bartolucci et al, 2006) did not change the orientation of His440 of the catalytic triad of TcAChE. In the latter cases, resistance of the carbamylated enzyme to spontaneous reactivation was rationalized by the existence of a strong hydrogen bond between the NH of the mono N-carbamyl moiety and the N 2 atom of the catalytic His440 that is required for catalysis.…”

Pharmacophoric Profile: Design of New Potential Drugs with PCA Analysis

“…Other drugs have been clinically studied and tested for use in the treatment of AD, such as physostigmine (Sippl, 2001;Ul-haq, 2010;Bartolucci, 2006). Some others are being tested and are promising candidates for the approval, including, Huperzine A (Patrick, 2005;Barak, 2005), metrifonate (Sippl, 2001) and phenserine (Sippl, 2001;Ul-haq, 2010).…”

Understanding Acetylcholinesterase Inhibitors: Computational Modeling Approaches

“…38,82,83 Some drugs are promising candidates and are in the testing phase and approval, among them, HUP, 64,81 metrifonate (MTR) 38 and phenserine (PHS). 38,82 Recently, another class of molecules that are dual AChE ligands was studied.…”