Catalysis enzyme models

D. Opportunities for Diversity-Based Methods in Biomimetic Oxidation Catalysis Enzyme Models and Enzymes... 

The field of synthetic enzyme models encompasses attempts to prepare enzymelike functional macromolecules by chemical synthesis [30]. One particularly relevant approach to such enzyme mimics concerns dendrimers, which are treelike synthetic macromolecules with a globular shape similar to a folded protein, and useful in a range of applications including catalysis [31]. Peptide dendrimers, which, like proteins, are composed of amino acids, are particularly well suited as mimics for proteins and enzymes [32]. These dendrimers can be prepared using combinatorial chemistry methods on solid support [33], similar to those used in the context of catalyst and ligand discovery programs in chemistry [34]. Peptide dendrimers used multivalency effects at the dendrimer surface to trigger cooperativity between amino acids, as has been observed in various esterase enzyme models [35]. 

The catalytic specificity of the cycloamyloses has led to their utilization as a model for understanding enzymatic catalysis. It is the authors expectation that the cycloamyloses will continue to serve as an enzyme model as well as a model for designing more efficient catalytic systems. Toward this end, it would seem profitable to pursue the idea that the cycloamyloses may lower the activation energy of a chemical reaction by inducing strain into the substrate. 

Allmendinger M (2004) PhD Thesis. Multi-Site Catalysis - Novel Strategies to Biodegradable Polyesters from Epoxides/CO and Macrocyclic Complexes as Enzyme Models. Universitat Ulm, Ulm... 

Enzyme has several unique characteristics—specific catalysis, regulation, biosynthesis, biodegradation, transport, etc. However, the first generation of enzyme models (or artificial enzymes) mostly deal with the simplest... 

Preparation and catalysis of disubstituted cyclodextrin as an excellent enzyme model is demonstrated by the RNAase model reported by Breslow et al. (68, 83). The enzyme models 10 and II, derived from 1, show a bellshaped pH versus rate profile for the hydrolysis of the cyclic phosphate of 4-terf-butylcatechol, indicating the cooperative catalysis by two imidazole groups (Fig. 21). The reactions catalyzed by 10 and II give exclusively 12 and 13, respectively. This interesting specificity indicates that the geometry of the P—O bond cleavage is quite different from each other. Another interesting enzyme-like kinetic behavior that these hosts exhibited is successful demonstration of the so-called bell-shaped pH profile. 

Breslow, R., How do imidazole groups catalyze the cleavage of RNA in enzyme models and enzymes Evidence from negative catalysis. Acc. Chem. Res. 24 317, 1991. 

H. Wada, H. Kagamiyama, T. Watanabe, In Pyridoxal Catalysis Enzymes and Model Systems (E. E. Snell, ed.) Wiley Interscience, New York, p. Ill (1966). 

Mechanism of imidazole catalysis of RNA cleavage by enzymes and enzyme models 91ACR317. 

Cytochrome P 450. The mechanism of P-450 catalysis is outlined in Figure 2 (3, 4). The mechanism is based on the stoichiometry, product analysis, and labeling experiments, quenching experiments, spectral evidence for the structures of intermediates involved, and model studies (enzyme models as well as oxidant models) of P-450 catalysis. 

COMPUTATIONAL ENZYMOLOGY INSIGHTS INTO ENZYME MECHANISM AND CATALYSIS FROM MODELLING... 

In heterogeneous catalysis these models are generally referred to as the Langmuir-Hinshelwood-Hougen-Watson (LHHW) models. The term Michaelis-Menten kinetics is often used in homogeneous catalysis, enzyme reactions and reactions of microbial systems. 

I Cyclodextrins are excellent enzyme models Catalysis and induced fit. Due to their cavities, which are able to accommodate guest (substrate) molecules, and due to the many hydroxyl groups lining this cavity, cyclodextrins can act catalytically in a variety of chemical reactions and they therefore serve as good model enzymes. Thus, benzoic acid esters are hydrolyzed in I aqueous solution by factors up to 100 times faster if cyclodextrins are added. The reaction in- j volves an acylated cyclodextrin as intermediate which is hydrolyzed in a second step of the j reaction, a mechanism reminiscent of the enzyme chymotrypsin. The catalytic efficiency can. be further enhanced if the cyclodextrins are suitably modified chemically so that a whole range of artificial enzymes have been synthesized [551-555, 556, 563, 564]. 

Ballester, Vidal-Ferran, and van Leeuwen evaluate concepts and strategies in the field of supramolecular catalysis. The authors describe what characterizes supramolecular catalysts, formulating a definition on the basis of the nature of interactions between catalyst and substrate or between building blocks of the catalyst. Examples are cited that demonstrate how supramolecular catalysts are superior to simple molecular catalysts in a broad range of reactions. Ballester et al. consider supramolecular catalysts as enzyme models, guided in their comparisons by the various mechanisms by which enzymes accelerate chemical transformations such as the binding of a reactant next to the catalytic site, the simultaneous complexation of two reactants, or desolvation. Addressing the synthesis of supramolecular catalysts, the authors describe how... 

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