Synthesis of novel N-benzyl substituted piperidine amides of 1H-indole-5-carboxylic acid as potential inhibitors of cholinesterases.

A series of novel N-benzyl substituted amides of 1H-indole-5-carboxylic acid were synthesized and evaluated for their ability to inhibit acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). The target compounds (6b-6e) displayed moderate potency to inhibit BuChE. One of the compounds tested, i.e., 1-benzylpiperidine amide of 1H-indole-5-carboxylic acid (6a) was a weak, non-selective inhibitor for both enzymes. The highest inhibitory activity towards BuChE (30.06% [10 microM]) was determined for compound (6c) which is 1-(3-chloro)benzylpiperidine amide of 1H-indole-5-carboxylic acid.

A novel expression cassette delivers efficient production of exclusively tetrameric human butyrylcholinesterase with improved pharmacokinetics for protection against organophosphate poisoning.

Butyrylcholinesterase is a stoichiometric bioscavenger against poisoning by organophosphorus pesticides and nerve agents. The low level of expression and extremely rapid clearance of monomeric recombinant human butyrylcholinesterase (rhBChE) from bloodstream (t½≈2 min) limits its pharmaceutical application. Recently (Ilyushin at al., PNAS, 2013) we described a long-acting polysialylated recombinant butyrylcholinesterase (rhBChE-CAO), stable in the bloodstream, that protects mice against 4.2 LD50 of VR. Here we report a set of modifications of the initial rhBChE expression vector to improve stability of the enzyme in the bloodstream and increase its production in CHO cells by introducing in the expression cassette: (i) the sequence of the natural human PRAD-peptide in frame with rhBChE gene via "self-processing" viral F2A peptide under control of an hEF/HTLV promoter, and (ii) previously predicted in silico MAR 1-68 and MAR X-29 sequences. This provides fully tetrameric rhBChE (4rhBChE) at 70 mg/l, that displays improved pharmacokinetics (t½ = 32 ± 1.2 h, MRT = 43 ± 2 h). 3D Fluorescent visualization and distribution of (125)I-labeled enzyme reveals similar low level 4rhBChE and rhBChE-CAO accumulation in muscle, fat, and brain. Administered 4rhBChE was mainly catabolized in the liver and breakdown products were excreted in kidney. Injection of 1.2 LD50 and 1.1 LD50 of paraoxon to BALB/c and knockout BChE-/- mice pre-treated with 4rhBChE (50 mg/kg) resulted in 100% and 78% survival, respectively, without perturbation of long-term behavior. In contrast, 100% mortality of non-pre-treated mice was observed. The high expression level of 4rhBChE in CHO cells permits consideration of this new expression system for manufacturing BChE as a biopharmaceutical.

Protein engineering of a human enzyme that hydrolyzes V and G nerve agents: design, construction and characterization.

Because of deficiencies in the present treatments for organophosphorus anticholinesterase poisoning, we are attempting to develop a catalytic scavenger that can be administered as prophylactic protection. Currently known enzymes are inadequate for this purpose because they have weak binding and slow turnover, so we are trying to make an appropriate enzyme by protein engineering techniques. One butyrylcholinesterase mutant, G117H, has the desired type of activity but reacts much too slowly. This communication describes an attempt to determine the reason for the slow reaction so that a more efficient enzyme might be designed. The results indicate that the mutation at residue 117 has resulted in a distortion of the transition state of the reaction of organophosphorus compounds with the active site serine. This information will be used to develop other mutants that avoid transition state stabilization sites.

Molecular dynamics and regulation of butyrylcholinesterase cholinergic activity by RNA binding proteins.

RNA recognition motif (RRM) is the most abundant RNA-binding domain, mainly known to involve in regulating post-transcriptional processes like intron splicing, stability and mRNA intracellular translocation. As RNA metabolism in neurons attributes a significant proportionality towards neurodegenerative diseases, potential role of RRM domains has become more conspicuous. Here, through flexible protein-protein docking and molecular dynamics simulation approaches, we postulate biochemically auspicious interactions occurring between Butyrylcholinesterase (BuChE) and RRM domains of transactive response DNA binding protein, embryonic lethal abnormal vision like protein 4 and heterogeneous nuclear ribonucleoprotein A1 protein. Through a comprehensive analysis of these interactions, we observed an exclusive binding behavior for RRM domains. Evidently, upon binding to RRMs, omega loop of BuChE attains a closed conformation and masks the access of substrate to the catalytic triad and oxyanion hole. Moreover, prominent adjustments were detected in RRM-bound BuChE at the peripheral anionic, choline binding and proton transfer sites. We propose that interaction of RNA-binding proteins to BuChE may decrease its ability to hydrolyze multiple choline esters, which may contribute in delayed progression of poor cognition during neurodegenerative disorders.