Enzymes play a key role in biological processes, as well as water serves as the solvent in which essentially all biochemical reactions take place. The synergy between protein structure and water relaxation dynamics is essential to address the underlying mechanism of enzymatic functionality [1]. As the mechanism of the reaction can be different in pure water than in the enzyme, one must not only consider the dynamical effects of altering the enzymatic micro-environment, but also that of water role in the catalysis mechanism [1, 2]. We examine the water micro-solvation behavior in a critical way, considering basically definitions, including the proposed effects as ''coupling between conformational and chemical motions,'' ''minimum energy pathway (MEP) searches'', ''entropy funnels'' and ''enzymatic reorganization energy'', as well as interplay with the experimental spectroscopy to verify the microsolvation water arrangement in enzyme, as illustrated in Figure 1. <img src='https://acs-archive-assets2.s3.amazonaws.com/241nm/uploads/66240_figure_1.jpg' alt='' /> . We focus the sophisticated proton and electron transfer processes, which respectively harness the energy pumping gradient and redox reaction, and are two key steps in metabolism, as well as controlling the signaling transduction [3]. Moreover the superb water sensing capability of newly-developed tryptophan analogue, (2,7-aza)Trp, (as depicted in ) in terms of excited-state proton transfer (ESPT) and ground-state tautomer equilibrium thus provides a tool for probing the water environment of a specific site in protein [4]. In combination with in-depth computer simulation, future quantitative correlation for the water microsolvation dynamics versus number/orientation of water molecules in enzyme is feasible, thus pave a way to shed light on the underlying mechanism with a molecular level understanding.References:[1] Wei-Chih Chao et al. J. Am. Chem. Soc. 2011 , 133, 18870.[2] Wei-Chih Chao et al. Biochemistry 2013 , 52, 1113.[3] Po-Hsien Huang et al. Science Signaling 2013 , 6, ra19[4] Jiun-Yi Shen et al. Nature Communication 2013 , 4, 2611.Figure Caption:figure 1. Resonance Raman (RR) spectra verify the induced-fit and conformational selection of lipid-derived signaling molecule by the water microsolvation in enzyme.figure 2. (2,7-aza)Trp exhibits remarkable triply-emission characteristic in probing water microsolvation dynamics in hemoproteins.

Exploring water micro-solvation dynamics: The missing link for understanding enzyme structure and catalysis

248th National Meeting (2014)

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