Metalloenzyme chemistry

Zn+2, Mn+2, Fe+2, Cd+2, Co+2, and Ni+2, although diminished activity results (35, 53). Fundamentally the enolase and aconitase reactions are closely related, since the net result of both is the addition or subtraction of a molecule of water. In spite of this similarity, the metal ions associated with these two reactions are very different. It is one of the puzzling aspects of metalloenzyme chemistry that every enzyme has a different metal ion specificity. Each of these enzymes is associated in its natural state with a specific metal ion, which differs from enzyme to enzyme. It is possible to remove the naturally occurring metal from many of these enzymes and to reactivate them by the addition of other metals, as has been shown in the case of carboxypeptidase. The order in which the various metal ions fall in their ability to activate the different enzymes again varies from enzyme to enzyme. 

Although rather rare in metalloenzyme chemistry, nucleophilic catalysis can be involved in reactions mediated by metalloporphyrin and metallocorrin complexes (e.g., vitamin B-12-dependent enzymes). 

King RB, Bitterwolf TE (2000) Metal carbonyl analogues of iron-sulfur clusters found in metalloenzyme chemistry. Coord Chem Rev 206-207 563-579... 

Chen, Y. L. Metalloenzyme Chemistry, Master Thesis, Texas A M University, 1989. 

Labarre JF (1978) Conformational Analysis in Inorganic Chemistry Semi-Empirical Quantum Calculation vs. Experiment. 35 1-35 Lammers M, Follmann H (1983) The Ribonucleotide Reductases A Unique Group of Metalloenzymes Essential for Cell Proliferation. 54 27-91 Le Brun NE, Thomson AJ, Moore GR (1997) Metal Centres of Bacterioferritins of Non-Heam-Iron-Containing Cyrochromes 6557. 88 103-138... 

Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602... 

As already mentioned, RNR is the metalloenzyme in which the first definitively characterized stable amino acid radical (1), later identified as a tyrosyl radical, was found in 1972. The RNR enzymes catalyse the reduction of ribonucleotides to their corresponding deoxyribonucleotides utilized in DNA biosynthesis. There are three unique classes of this enzyme, differing in composition and cofactor requirements all of them, however, make use of metal ions and free radical chemistry. Excellent reviews on RNRs are available (60, 61, 70, 89-97). 

Many transition metal complexes are able to fix small molecules such as O2, N2, CO, C02, and S02. Interest in this aspect of inorganic chemistry is largely related to the role that metalloenzymes play in catalysing redox reactions of the type shown in Scheme 1. 

Michael K. Johnson Department of Chemistry Center for Metalloenzyme Studies University of Georgia Athens, GA 30602 USA... 

Haase, W. Walz, L. Nepveu, F. In The Coordination Chemistry of Metalloenzymes Bertini, I., Drago, R.S., Luchinat, C., Eds. D. Reldel Publishing Company Holland, 1983, pp. 229-34. Sheldon, R.A. Kochi, J.K. Hetal Catalyzed Oxidations of Organic Compounds, Academic New York, 1981. 

---