Review of Genetic Variants of Butyrylcholinesterase and Their Potential Impact on Human Health

Butyrylcholinesterase (BChE) is an enzyme found in plasma and many other parts of the body. It is enzyme that hydrolyses drugs containing ester bonds such as drugs acting at the neuromuscular junction (succinylcholine) and local anaesthetics (procaine). Examination of the gene for mutations or polymorphisms causing the observed biochemical phenotypes has isolated those responsible for all the most widely known variants. The molecular bases of several genetic variants of BChE have been reported, such as the Atypical variant, fluoride-resistant variant, silent variant, K variant, J variant and C5 variant. In general, BChE polymorphisms have been shown to produce enzymes with varying levels of catalytic activity. Genetic variants of human butyrylcholinesterase were one of the first examples in the new field of pharmacogenetics when it was recognized that abnormal response to the succinylcholine was due to a mutated enzyme with low binding affinity. Beside that, variant of BChE has potential impact for Alzheimer disease patology.

Review of Genetic Variants of Butyrylcholinesterase and Their Potential Impact on Human Health

Butyrylcholinesterase (BChE) is an enzyme found in plasma and many other parts of the body. It is enzyme that hydrolyses drugs containing ester bonds such as drugs acting at the neuromuscular junction (succinylcholine) and local anaesthetics (procaine). Examination of the gene for mutations or polymorphisms causing the observed biochemical phenotypes has isolated those responsible for all the most widely known variants. The molecular bases of several genetic variants of BChE have been reported, such as the Atypical variant, fluoride-resistant variant, silent variant, K variant, J variant and C5 variant. In general, BChE polymorphisms have been shown to produce enzymes with varying levels of catalytic activity. Genetic variants of human butyrylcholinesterase were one of the first examples in the new field of pharmacogenetics when it was recognized that abnormal response to the succinylcholine was due to a mutated enzyme with low binding affinity. Beside that, variant of BChE has potential impact for Alzheimer disease patology.

Review of Genetic Variants of Butyrylcholinesterase and Their Potential Impact on Human Health

Butyrylcholinesterase (BChE) is an enzyme found in plasma and many other parts of the body. It is enzyme that hydrolyses drugs containing ester bonds such as drugs acting at the neuromuscular junction (succinylcholine) and local anaesthetics (procaine). Examination of the gene for mutations or polymorphisms causing the observed biochemical phenotypes has isolated those responsible for all the most widely known variants. The molecular bases of several genetic variants of BChE have been reported, such as the Atypical variant, fluoride-resistant variant, silent variant, K variant, J variant and C5 variant. In general, BChE polymorphisms have been shown to produce enzymes with varying levels of catalytic activity. Genetic variants of human butyrylcholinesterase were one of the first examples in the new field of pharmacogenetics when it was recognized that abnormal response to the succinylcholine was due to a mutated enzyme with low binding affinity. Beside that, variant of BChE has potential impact for Alzheimer disease patology

Non-quaternary oximes detoxify nerve agents and reactivate nerve agent-inhibited human butyrylcholinesterase

Government-sanctioned use of nerve agents (NA) has escalated dramatically in recent years. Oxime reactivators of organophosphate (OP)-inhibited acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) serve as antidotes toward poisoning by OPNAs. The oximes used as therapeutics are quaternary compounds that cannot penetrate the blood–brain barrier (BBB). There remains an urgent need for the development of next generation OPNA therapeutics. We have developed two high-throughput screening (HTS) assays using a fluorogenic NA surrogate, O-ethyl methylphosphonyl O-4-methyl-3-cyano-coumarin (EMP-MeCyC). EMP-MeCyC detoxification and EMP-BChE reactivation screening campaigns of ~155,000 small molecules resulted in the identification of 33 nucleophile candidates, including non-quaternary oximes. Four of the oximes were reactivators of both Sarin- and VX-inhibited BChE and directly detoxified Sarin. One oxime also detoxified VX. The novel reactivators included a non-quaternary pyridine amidoxime, benzamidoxime, benzaldoxime and a piperidyl-ketoxime. The VX-inhibited BChE reactivation reaction rates by these novel molecules were similar to those observed with known bis-quaternary reactivators and faster than mono-quaternary pyridinium oximes. Notably, we discovered the first ketoxime reactivator of OP-ChEs and detoxifier of OPNAs. Preliminary toxicological studies demonstrated that the newly discovered non-quaternary oximes were relatively non-toxic in mice. The discovery of unique non-quaternary oximes opens the door to the design of novel therapeutics and decontamination agents following OPNA exposure.

Effects of Kifunensine on Production and N-Glycosylation Modification of Butyrylcholinesterase in a Transgenic Rice Cell Culture Bioreactor

The production and N-glycosylation of recombinant human butyrylcholinesterase (BChE), a model highly glycosylated therapeutic protein, in a transgenic rice cell suspension culture treated with kifunensine, a strong α-mannosidase I inhibitor, was studied in a 5 L bioreactor. A media exchange was performed at day 7 of cultivation by removing spent sugar-rich medium (NB+S) and adding fresh sugar-free (NB-S) medium to induce the rice α-amylase 3D (RAmy3D) promoter to produce rice recombinant human BChE (rrBChE). Using a 1.25X-concentrated sugar-free medium together with an 80% reduced working volume during the media exchange led to a total active rrBChE production level of 79 ± 2 µg (g FW)−1 or 7.5 ± 0.4 mg L−1 in the presence of kifunensine, which was 1.5-times higher than our previous bioreactor runs using normal sugar-free (NB-S) media with no kifunensine treatment. Importantly, the amount of secreted active rrBChE in culture medium was enhanced in the presence of kifunensine, comprising 44% of the total active rrBChE at day 5 following induction. Coomassie-stained SDS-PAGE gel and Western blot analyses revealed different electrophoretic migration of purified rrBChE bands with and without kifunensine treatment, which was attributed to different N-glycoforms. N-Glycosylation analysis showed substantially increased oligomannose glycans (Man5/6/7/8) in rrBChE treated with kifunensine compared to controls. However, the mass-transfer limitation of kifunensine was likely the major reason for incomplete inhibition of α-mannosidase I in this bioreactor study.

Effects of Kifunensine on Production and N-glycosylation Modification of Butyrylcholinesterase in a Transgenic Rice Cell Culture Bioreactor

The production and N-glycosylation of recombinant human butyrylcholinesterase (BChE), a model highly glycosylated therapeutic protein, in a transgenic rice cell suspension culture treated with kifunensine, a strong α-mannosidase I inhibitor, was studied in a 5 L bioreactor. A media exchange was performed at day 7 of cultivation by removing spent sugar rich media (NB+S) and adding fresh sugar free (NB-S) media to induce the rice α-amylase 3D (RAmy3D) promoter to produce rice recombinant human BChE (rrBChE). Using a 1.25X concentrated sugar-free medium together with an 80% reduced working volume during the media exchange lead to a total active rrBChE production level of 79 ± 2 µg (g FW)-1 or 7.5 ± 0.4 mg L-1 in the presence of kifunensine, which is 1.5-times higher than our previous bioreactor runs using normal sugar free medium with no kifunensine treatment. Importantly, the amount of secreted active rrBChE in culture medium was enhanced in the presence of kifunensine, comprising 44% of the total active rrBChE at day 5 post-induction. Coomassie stained SDS-PAGE gel and Western blot analyses reveal different electrophoretic migration of purified rrBChE bands with and without kifunensine treatment, which is attributed to different N-glycoforms. N-Glycosylation analysis shows substantial increase of oligomannose glycans (Man5/6/7/8) in rrBChE treated with kifunensine compared to controls. However, mass transfer limitation of kifunensine is likely the major reason for incomplete inhibition of α-mannosidase I in this bioreactor study.

Signature Ions in MS/MS Spectra for Dansyl-Aminohexyl-QQIV Adducts on Lysine

Bacterial transglutaminase was used to label human plasma proteins with fluorescent tags. Protein lysines were modified with dansyl-epsilon-aminohexyl-Gln-Gln-Ile-Val-OH (dansylQQIV), while protein glutamines were modified with dansyl cadaverine. Labeled proteins included human butyrylcholinesterase, apolipoprotein A-1, haptoglobin, haptoglobin-related protein, immunoglobulin heavy chain, and hemopexin. Tryptic peptides were analyzed by LC-MS/MS on an Orbitrap Fusion Lumos mass spectrometer. Modified residues were identified in Protein Prospector and Proteome Discoverer searches of mass spectrometry data. The MS/MS fragmentation spectra from dansylQQIV-modified peptides gave intense peaks at 475.2015, 364.1691, 347.1426, 234.0585, and 170.0965 m/z. These signature ions are useful markers for identifying modified peptides. Human butyrylcholinesterase retained full activity following modification by dansylQQIV or dansyl cadaverine.