Metalloenzyme catalysis

Metalloenzyme Catalysis Joseph J. Villafranca and Frank M. Raushel... 

This enzyme has been studied extensively by x-ray, kinetic, NMR, optical, circular dichroic, and fluorescence techniques. Thus, many approaches have been used to explore the role of the metal ions in catalysis and of other protein residues in substrate binding and catalysis. The review of this enzyme will serve to point out the information to be gained from using multiple biophysical approaches in understanding metalloenzyme catalysis. 

In order to gain insights into the molecular mechanisms of metalloenzyme catalysis it is necessary to have an understanding of the fundamental processes involved in catalysis by simple metal salts and their coordination complexes. 

Likhtenshtein G.I. (1988a) Chemical Physics of Redox Metalloenzyme Catalysis, Springer-Verlag, Berlin. 

Hansen, A.G., Zhang, J.D., Christensen, H.E.M., Welinder, A.C., Wackerbarth, H., and Ulstrup, J. (2004) Electron transfer and redox metalloenzyme catalysis at the single-molecule level. Israel Journal of Chemistry, 44, 89-100. 

It is estimated that approximately one-third of all enzyme-catalyzed reactions require a metal ion or ions for catalytic activity. The functions of these metal ions can be placed in three broad categories (1) structural integrity (no specific catalytic function), (2) electron transfer reactions, and (3) electrophilic catalysis. The latter of these broad classes of function/structure will be the focus of this chapter, in which we will explore current data and theories of metalloenzyme catalysis. 

Key words. Metalloenzymes, catalysis, oxidation, nickel, alkene. 

The steady state kinetics and thermodynamic activation constants of the heptamolybdate ion-catalised glucose-mannose epimerization, a model for metalloenzyme catalysis, have been determined for both directions of the reaction. ... 

Fig. 17.11. Theoretical dependences of the synchronization factor (asyn) on the number of degrees of freedom (n) of the nuclei involved in a concerted reaction. The curves have been constracted in accordance with Eqs 2.44 and 2.45. (Likhtenshtein, G.I., Chemical Physics of Redox Metalloenzyme Catalysis, Springer-Verlag, Berlin.. 1988). Reproduced with permission...

Fig. 18.6. The energy profile of a nitrogenase reaction. Eq is the standard redox potential of the reactants, intermediates and products of the reaction Fd = foredoxin FeP = Fe protein FeMo = FeMo protein. The arrow indicates the increase of the reduction potential upon ATP hydrolysis (Likhtenshtein G.I. Chemical Physics of Redox Metalloenzyme Catalysis, Springer-Verlag, Berlin, 1988). Reproduced wiA permission.

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