Entatic

Fig. 10. Examples of coordination geometry in the entatic state (34) where the Lewis acidity of Zn(II) in its metalloprotein is considerably altered as compared with that for (a) the Zn2t aquo ion (30), (b) Zn(II) in alcohol dehydrogenase, (c) Zn(II) in carbonic anhydrase, and (d) Zn(II) in carboxypeptidase. Redrawn after Ref. (22).

Vallee, B.L. and Williams RJ. (1968) Metalloenzymes the entatic nature of their active sites. Proc. Natl. Acad. Sci. USA, 59, 498-505. 

Fig. 8.2 Ori entations of an amide NH dipolar coupling bond-vector of the protein ubiquitin. Each cone of orientations is compatible with two different alignment directions adopted by the protein in two different alignment media. The central lines defining each cone correspond to the orientations obtained from the measured dipolar couplings. The outer lines include orientations that are possible if the dipolar coupling values are either increased or decreased by 1 Hz. The angle at which the two cones intersect is defined by ft. The solid dot at the cone intersection determines the orientation of the dipolar coupling vector. (Reproduced with permission from B. E. Ramirez and A. Bax, J. Am. Chem. Soc. 1998, 720, 9106-9107.)...

Anyhow, our study has demonstrated the benefit of "strained" polymeric catalyst-substrate complexes, a phenomenon well-known in enzymology (26) and once indicated by the term "entatic state" (16). 

A hypothetical conformational state defined by a geometrically and electronically strained site within an enzyme thought to facilitate the conversion of an enzyme-substrate complex to the transition state. Vallee and Williams defined the entatic state as an abnormal condition of localized strain transmitted by relief of compression or other steric clashes elsewhere in the enzyme. They suggested that catalytic rate enhancements arise from the heightened reactivity of catalytic group(s) that have experienced unimolecular activation. Williams ... 

Ensemble average fluctuation with time, CORRELATION FUNCTION ENTATIC STATE ENTERING GROUP ENTEROPEPTIDASE ENTEROTOXIN ENTHALPY... 

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