Activity and molecular dynamics relationship within the family of human cholinesterases

Abstract

The temperature dependence of the dynamics of recombinant human acetylcholinesterase (hAChE) and plasma human butyrylcholinesterase (hBChE) is examined using elastic incoherent neutron scattering. These two enzymes belong to the same family and present 50% amino acid sequence identity. However, significantly higher flexibility and catalytic activity of hAChE when compared to the ones of hBChE are measured. At the same time, the average height of the potential barrier to the motions is increased in the hBChE, e.g. more thermal energy is needed to cross it in the latter case, which might be the origin of the increase in activation energy and the reduction in the catalytic rate of hBChE observed experimentally. These results suggest that the motions on the picosecond timescale may act as a lubricant for those associated with activity occurring on a slower millisecond timescale.

Motional heterogeneity in human acetylcholinesterase revealed by a non-Gaussian model for elastic incoherent neutron scattering

“…The experimental data used in the present study have been obtained from D 2 O-hydrated protein powders. 12 Since the cross section for incoherent scattering from hydrogen atoms is dominant and since hydrogen atoms make up about 50% of the total number of atoms in a protein, the measured dynamic structure factor can be approximated as…”

“…According to Eqs. (10) and (12) the model EISF is the generating function for the moments and cumulants of λ =ũ 2 :…”

“…Elastic neutron scattering data on different cholinesterases have been recently analyzed with the widely used Gaussian model. [12][13][14]…”

Correlation of the dynamics of native human acetylcholinesterase and its inhibited huperzine A counterpart from sub-picoseconds to nanoseconds

“…Production, purification and sample preparation of recombinant hAChE with or without two molar equivalents of (2)-HupA (http://www.sigmaaldrich.com/sigma-aldrich/ home.html, H5902(-)) are described in more detail by Peters et al [26]. Briefly, after a lyophilization step, the protein powders were placed in aluminium sample containers, dried over P 2 O 5 and re-hydrated from D 2 O vapour exchange to a final water content of 0.4 g water/g protein.…”

“…Are differences in catalytic activities reflected in variations in atomic thermal fluctuations on the pico-to nanosecond timescale? The first evidence supporting this hypothesis comes from comparative studies on hAChE, human butyrylcholinesterase (hBChE) [26] and mAChE [27]. In a next step, we wanted to block enzymatic activity with an inhibitor to probe its effects on the dynamics.…”