title: Characterization of a novel butyrylcholinesterase point mutation (p.Ala34Val), "silent" with mivacurium.
abstract: Butyrylcholinesterase deficiency is characterized by prolonged apnea after the use of muscle relaxants (suxamethonium or mivarcurium) in patients who have mutations in the BCHE gene. Here, we report a case of prolonged neuromuscular block after administration of mivacurium leading to the discovery of a novel BCHE variant (c.185C>T, p.Ala34Val). Inhibition studies, kinetic analysis and molecular dynamics were undertaken to understand how this mutation remote from the active center determines the "silent" phenotype. Low activity of patient plasma butyrylcholinesterase with butyrylthiocholine (BTC) and benzoylcholine, and values of dibucaine and fluoride numbers fit with a heterozygous enzyme of type atypical/silent. Kinetic analysis with succinyldithiocholine (SCdTC) as the substrate showed that Ala34Val BChE was inactive against this substrate. However, with BTC, the mutant enzyme was active, displaying an unexpected activation by excess substrate. Competitive inhibition of BTC by mivacurium gave a Ki=1.35 mM consistent with the lack of activity with the related substrate SCdTC, and with the clinical data. Molecular dynamic simulations revealed the mechanism by which mutation Ala34Val determines the silent phenotype: a chain of intramolecular events leads to disruption of the catalytic triad, so that His438 no longer interacts with Ser198, but instead forms hydrogen bonds either with residues Glu197 and Trp82, or peripheral site residue Tyr332. However, at high BTC concentration, initial binding of substrate to the peripheral site triggers restoration of a functional catalytic triad, and activity with BTC.
authors.affiliation: Bégin Military Teaching Hospital, Department of Biology, Unit of Human Genetics, 69 Paris Av. 94 163 Saint Mandé, France. Electronic address: isabelle.mabboux@etu.upmc.fr.
authors.forename: Herve
authors.initials: H
authors.lastname: Delacour
authors.affiliation: Modeling of Biomolecules Lab., N.M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, 4 Kosygina St., 119334 Moscow, Russia. Electronic address: sofya.lushchekina@gmail.com.
authors.forename: Sofya
authors.initials: S
authors.lastname: Lushchekina
authors.affiliation: Bégin Military Teaching Hospital, Department of Biology, Unit of Human Genetics, 69 Paris Av. 94 163 Saint Mandé, France. Electronic address: isabelle.mabboux@etu.upmc.fr.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Mabboux
authors.affiliation: Bégin Military Teaching Hospital, Department of Biology, Unit of Human Genetics, 69 Paris Av. 94 163 Saint Mandé, France. Electronic address: franck.ceppa@santarm.fr.
authors.forename: Franck
authors.initials: F
authors.lastname: Ceppa
authors.affiliation: Neuropharmacology Laboratory, Kazan Federal University, 18 Kremlevskaya St., 420008 Kazan, Russia; Eppley Institute, University of Nebraska Medical Center, Omaha, NE 68198-5950, USA. Electronic address: pmasson@unmc.edu.
authors.forename: Patrick
authors.initials: P
authors.lastname: Masson
authors.affiliation: Eppley Institute, University of Nebraska Medical Center, Omaha, NE 68198-5950, USA. Electronic address: lmschopf@unmc.edu.
authors.forename: Lawrence M
authors.initials: LM
authors.lastname: Schopfer
authors.affiliation: Eppley Institute, University of Nebraska Medical Center, Omaha, NE 68198-5950, USA. Electronic address: olockrid@unmc.edu.
authors.forename: Oksana
authors.initials: O
authors.lastname: Lockridge
mesh_terms: D000368:Aged; D002091:Butyrylcholinesterase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002092:Butyrylthiocholine / Q000378:metabolism; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D005260:Female; D006579:Heterozygote; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology* / Q000627:therapeutic use; D008297:Male; D000077590:Mivacurium; D056004:Molecular Dynamics Simulation; D003473:Neuromuscular Nondepolarizing Agents / Q000494:pharmacology / Q000627:therapeutic use; D010375:Pedigree; D017354:Point Mutation; D013390:Succinylcholine / Q000494:pharmacology
chemical_list: D002800:Cholinesterase Inhibitors; D007546:Isoquinolines; D003473:Neuromuscular Nondepolarizing Agents; D002092:Butyrylthiocholine; D000077590:Mivacurium; D002091:Butyrylcholinesterase; D013390:Succinylcholine
keywords: Butyrylcholinesterase deficiency; Genetic diagnosis