Masson_1997_Biochem.J_325_53

Reference

Title : Importance of aspartate-70 in organophosphate inhibition, oxime re-activation and aging of human butyrylcholinesterase - Masson_1997_Biochem.J_325_53
Author(s) : Masson P , Froment MT , Bartels CF , Lockridge O
Ref : Biochemical Journal , 325 :53 , 1997
Abstract :

Asp-70 is the defining amino acid in the peripheral anionic site of human butyrylcholinesterase (BCHE), whereas acetylcholinesterase has several additional amino acids, the most important one being Trp-277 (Trp-279 in Torpedo AChE). We studied mutants D70G, D70K and A277W to evaluate the role of Asp-70 and Trp-277 in reactions with organophosphates. We found that Asp-70 was important for binding positively charged echothiophate, but not neutral paraoxon and iso-OMPA. Asp-70 was also important for binding of positively charged pralidoxime (2-PAM) and for activation of re-activation by excess 2-PAM. Excess 2-PAM had an effect similar to substrate activation, suggesting the binding of 2 mol of 2-PAM to wild-type but not to the D70G mutant. A surprising result was that Asp-70 was important for irreversible aging, the D70G mutant having a 3- and 8-fold lower rate of aging for paraoxon-inhibited and di-isopropyl fluorophosphate-inhibited BCHE. Mutants of Asp-70 had the same rate constants for phosphorylation and re-activation by 2-PAM as wild-type. The A277W mutant behaved like wild-type in all assays. Our results predict that people with the atypical (D70G) variant of BCHE will be more sensitive to the toxic effects of echothiophate, but will be equally sensitive to paraoxon and di-isopropyl fluorophosphate. People with the D70G mutation will be resistant to re-activation of their inhibited BCHE by 2-PAM, but this will be offset by the lower rate of irreversible aging of inhibited BCHE, allowing some regeneration by spontaneous hydrolysis.

PubMedSearch : Masson_1997_Biochem.J_325_53
PubMedID: 9224629

Related information

Mutation D70G_human-BCHE    D70K_human-BCHE    A277W_human-BCHE
Inhibitor D70G_human-BCHE    D70K_human-BCHE    A277W_human-BCHE    DFP    Echothiophate    Paraoxon
Reactivator D70G_human-BCHE    D70K_human-BCHE    A277W_human-BCHE    DFP    Echothiophate    Paraoxon    2-PAM

Citations formats

Masson P, Froment MT, Bartels CF, Lockridge O (1997)
Importance of aspartate-70 in organophosphate inhibition, oxime re-activation and aging of human butyrylcholinesterase
Biochemical Journal 325 :53

Masson P, Froment MT, Bartels CF, Lockridge O (1997)
Biochemical Journal 325 :53