3 publications

3 publications

Diiron-Containing Metalloproteins: Developing Functional Models

Review

DeGrado, W.F.; Lombardi, A.

C. R. Chim. 2007, 10, 703-720, 10.1016/j.crci.2007.03.010

A major objective in protein science is the design of enzymes with novel catalytic activities that are tailored to specific applications. Such enzymes may have great potential in biocatalysis and biosensor technology, such as in degradation of pollutants and biomass, and in drug and food processing. To reach this objective, investigations into the basic biochemical functioning of metalloproteins are still required. In this perspective, metalloprotein design provides a powerful approach first to contribute to a more comprehensive understanding of the way metalloproteins function in biology, with the ultimate goal of developing novel biocatalysts and sensing devices. Metalloprotein mimetics have been developed through the introduction of novel metal-binding sites into naturally occurring proteins as well as through de novo protein design. We have approached the challenge of reproducing metalloprotein active sites by using a miniaturization process. We centered our attention on iron-containing proteins, and we developed models for heme proteins and diiron–oxo proteins. In this paper we summarize the results we obtained on the design, structural, and functional properties of DFs, a family of artificial diiron proteins.


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New Biocatalysts Mimicking Oxidative Hemoproteins: Hemoabzymes

Review

Mahy, J.-P.

C. R. Chim. 2007, 10, 684-702, 10.1016/j.crci.2006.12.014

Catalytic antibodies with a metalloporphyrin cofactor or “hemoabzymes”, used as models for hemoproteins like peroxidases and cytochrome P450s, represent a promising route to catalysts tailored for selective oxidation reactions. The first strategy has been to produce anti-porphyrin antibodies, raised against various N-substituted- and meso-carboxyaryl-porphyrins, which led to monoclonal antibodies exhibiting, in the presence of the corresponding iron-porphyrin cofactor, a significant peroxidase activity. We ourselves obtained an artificial hemoprotein by associating a monoclonal antibody, 13G10, and its iron(III)-α,α,α,β-meso-tetrakis(ortho-carboxyphenyl)porphyrin (Fe(ToCPP)) hapten, which exhibited a significant peroxidase activity. Biological studies suggested that in this antibody, a carboxylic acid side chain of the protein participated in the catalysis, but no amino acid residue acting as an axial ligand of the iron was detected. Therefore, to provide the iron atom with an axial ligand, we raised antibodies against microperoxidase 8, a heme octapeptide containing a histidine bound to the iron atom. This strategy was successful, as an antibody–microperoxidase 8 complex (3A3–MP8) led to the best kcat/Km ever reported for antibody–porphyrin complexes. The ability of the 3A3–MP8 complex to catalyze the selective oxidation of substrates was studied and it was found able to catalyze the regioselective nitration of aromatics by NO2−/H2O2 as well as the stereoselective oxidation of sulfides like thioanisole by H2O2. Other strategies based on antibodies have to be developed to obtain more efficient biomimetic systems for cytochrome P450s. A first one could involve the modification of anti-substrate antibodies by covalent linkage of an iron(III)-porphyrin close to the binding site of the substrate, to obtain an artificial hemoprotein able to catalyze its regioselective oxidation.


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Second-Generation Artificial Hydrogenases Based on the Biotin-Avidin Technology: Improving Selectivity and Organic Solvent Tolerance by Introduction of an (R)-Proline Spacer

Ward, T.R.

C. R. Chim. 2007, 10, 678-683, 10.1016/j.crci.2007.02.020

We report on our efforts to create efficient artificial metalloenzymes for the enantioselective hydrogenation of N-protected dehydroamino acids using streptavidin as host protein. Introduction of an (R)-proline spacer between the biotin anchor and the diphosphine moiety affords a versatile ligand Biot-(R)-Pro-1 which displays good (S)-selectivities in the presence of streptavidin (91% ee). The resulting artificial metalloenzyme [Rh(Biot-(R)-Pro-1)(COD)]+ ⊂ WT-Sav displays increased stability against organic solvents.


Metal: Rh
Ligand type: Phosphine
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical
Reaction: Hydrogenation
Max TON: ---
ee: 94
PDB: ---
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