Active site topography

The ability to both exist in a stable basal state and generate sufficiently oxidizing intermediates in order to specifically transform substrates is the challenge that heme peroxidases face. Redox potential (E°) play a critical role in determining a peroxidase ability to catalyze challenging oxidation reactions. However, it is not the only factor. As in other heme proteins, activity also depends on electrostatic interactions, substrate orientation, and active site topography [2],... 

The peptidase inhibitors, (82) and (83), are actually amino acid and transition-state mimics pieced together to emulate the typical ligand-bound extended p-strand inhibitor conformation. The structurally distinct heterocyclic aspartic protease inhibitors (85-86) and (87-88) are non-peptide peptidomimetics because of their remote structural relationship to native peptide substrates. Yet these two distinct peptidomimeticclasses bind to the same active site topography. These structurally distinct peptidomimetics selectively stabilize closely related enzyme conformations. 

A new sorbent for the biospecific chromatography of serine proteinases has been obtained via attachment of p-(reversible inhibition by organoboronic acids has been used to study the active site topography of subtilisin. ... 

Substrate specificity differences between boar acrosin and trypsin are not particularly manifest when using small substrates, but these enzymes show distinctly different kinetics of porcine ZP hydrolysis (34). The loss of 30% mass in the conversion from m - to m -acrosin has little effect on the kinetic analyses of inhibition and substrate preference with artificial substrates and small trypsin inhibitors, indicating that this excised portion of the enzyme contributes little to the topography of the active site (35). From Km analyses with amide and ester substrates of Arg and Lys, acrBSin prefers the Arg substrates over Lys, and Km differences between amide and ester substrates indicates that ac Ssin proceeds kinetically through a classical double displacement mechanism as does trypsin (36). 

Group A active sites correspond to the (3 states of TDS, arising from CO dissociative adsorption. The topography of these active sites is random, as the values of the lateral interaction energy, jS, are negative. The B and C groups of active sites shown in our plots correspond to the oc states of TDS. They are characterized... 

The RF-GC methodology is technically very simple and it is combined with a mathematical analysis that gives the possibility for the estimation of various physicochemical parameters related to solid catalysts characterization in a simple experiment under conditions compatible with the operation of real catalysts. The experimentally determined kinetic quantities are not only consistent with the results of other techniques, but, moreover, they can give important information about the mechanism of the relevant processes, the nature of the active sites, and the topography of the heterogeneous surfaces. 

Let us assume the patchwise topography for active sites and take into account the lateral interactions between the neighbouring chemisorbed species in the mean-field approximation [32]. Then, the interaction potential between the first-order neighbouring... 

The modeling results lead to the conclusion that NTE and AChE, two major OP target enzymes, differ considerably in the topography of their active sites and have different structural and physicochemical requirements for their respective OP inhibitors. 

Models which regard solid surfaces as non-uniform, in the sense of containing different sub-sets of surface sites distinguishable from each other by virtue of their local structure and topography, and which associate widely different activities with these subsets, have long been termed active-site models [31—33]. The applicability of this type of model to individual catalysed reactions has been the subject of controversy [12b],... 

Nitrile, Isonitrile, and Alkyne Analogs. Exploration of N2ase-catalyzed reductions of selected nitrile, isonitrile, and alkyne analogs provides examples of novel chemical reactions and yields information about the topography of the active sites of Noase. 

The SOD molecule exerts an extensive surface topography of sequence-conserved residues, suggesting that this invariance is critical to the enzymatic function Two pits are seen, forming specific binding sides in the narrowest part of the active-site channel floor. One pit (the Cu-site) is formed by the exposed surface of the Cu(ll) and parts of His-61, His-118, Thr-135 and Arg-141. The adjacent pit (the water-site) is formed by parts of the exposed surface of Thr-135, Gly-136, Ala-138, Gly-139 and Cu-ligands His-44 and His-118. Oj" fit the Cu-site surface with one oxygen bound to the Cu and the other H-bonded to Arg-141. Both active-site channel pits contain highly ordered water molecules. 

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