Noodleman and Coworkers

This review will give a subjective account of mechanistic studies on some representative zinc enzymes comprising the enzyme classes I-IV (oxidoreductases, transferases, hydrolases and lyases). It does not claim to be comprehensive, as a comprehensive review would be far too extensive for this work. Lowther and Matthews have reviewed the met-alloaminopeptidases and Noodleman and coworkers have reviewed calculational studies on metalloenzymes. We apologize in advance for any omissions and point to previous reviews on this and related subjects to be found, e.g., in References 7-11. 

The electronic stmcture, spectroscopy, and reduction potential have been thoroughly studied for all common classes of iron-sulphur clusters [52,89,182-191]. In particular, Noodleman and coworkers have performed detailed quantum chemical calculations on iron-sulphur clusters in various spin states [192-198]. It is now settled that rubredoxin contains an iron ion in the high-spin state (quintet for Fe , sextet for Fe ), whereas in the [2Fe-2S] clusters, the two iron ions are both in the high-spin state, but antiferromagntically coupled to form a singlet or doublet state for the oxidised (Ill+ni) and reduced (mixed-valence n+ni) forms, respectively [112,162]. In variance to the Cua site, the unpaired spin is trapped at one of the iron ions in the mixed-valence state. 

Figure 6.15 Geometries of allyl alcohol adducts at the FeMoco as calculated by Noodleman and coworkers with relative energies and hyperflne coupling constantsReproduced with permission from ref. 149. Copyright 2008 American Chemical Society.

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