Enzymes catalytic power

All these uses depend upon one or both of the two paramount properties of enzymes catalytic power and specificity. 

Roca, M. Marti, S. Andres, J. Moliner, V. Tunon, I. Bertran, J. Williams, I. H. Theoretical modeling of enzyme catalytic power Analysis of cratic and electrostatic factors in catechol O-methyltransferase, J. Am. Chem. Soc. 2003,125,1126-1131. 

Kinetic Baselines for Estimations of Enzyme Catalytic Power... 

Chart 4.1. Measures of enzyme catalytic power for a unireactant enzyme. 

Appendix The Use of Model Reactions to Estimate Enzyme Catalytic Power 1071... 

The kinetic investigation of enzymic reactions and suitable non-enzymic standard reactions permits, as just described, the numerical calculation of measures of enzyme catalytic power. These measures are ratios of rate constants and they correspond to equilibrium constants for reactions of free enzyme or enzyme complexes with the transition state for the standard reaction to generate complexes of the enzyme with various transition states along the enzymic reaction pathway, sometimes with liberation of other ligands (see the examples above). 

Novel kinetic formulations. The description given above of the calculation of measures of enzyme catalytic power relies initially on empirically determined rate constants for enzymic and non-enzymic reactions. The numerical results at the initial stage are therefore theory-free and may be used for many purposes with perfect confidence. 

In this way, the main computational challenge in the determination of the enzyme catalytic power is reduced to the calculation of the rate constant, which can be expressed, according to Eyring s transition state theory (TST) as... 

It is clear that in a qualitative sense, the factors outlined in this section help us to understand the origin of enzyme catalytic power. However, it is not clear that for any given enzyme we can yet account quantitatively for the magnitude of its rate enhancement. 

Neet, K. E. "Enzyme Catalytic Power Minireview Series." /. Biol. Chem., 273,25527-27038 (1998). 

Koshland (1976) has considered the evolution of enzyme catalytic power from the point of view of the sequential acquisition of catalytic ability, specificity, regulability, and cooperativity. He contends that function is the driving force of evolution and must be subject to incremental improvements by small changes in structure, such incremental modifications occurring in a random manner. 

Many enzymes (see Chapters 14 to 16) derive at least some of their catalytic power from oligomeric associations of monomer subunits. This can happen in several ways. The monomer may not constitute a complete enzyme active site. Formation of the oligomer may bring ail the necessary catalytic groups together to form an active enzyme. For example, the active sites of bacterial glutamine synthetase are formed from pairs of adjacent subunits. The dissociated monomers are inactive. 

Enzymes are characterized by three distinctive features catalytic power, specificity, and regulation. 

Enzymes display enormous catalytic power, accelerating reaction rates as much as lO over uncatalyzed levels, which is far greater than any synthetic catalysts can achieve, and enzymes accomplish these astounding feats in dilute aqueous... 

This idea also helps to explain some of the mystery surrounding the enormous catalytic power of enzymes In enzyme catalysis, precise orientation of catalytic residues comprising the active site is necessary for the reaction to occur substrate binding induces this precise orientation by the changes it causes in the protein s conformation. 

In Chapter 16, we explore in greater detail the factors that contribute to the remarkable catalytic power of enzymes and examine specific examples of enzyme reaction mechanisms. Here we focus on another essential feature of enzymes the regulation of their aetimty. 

The specificity of enzyme reactions can be altered by varying the solvent system. For example, the addition of water-miscible organic co-solvents may improve the selectivity of hydrolase enzymes. Medium engineering is also important for synthetic reactions performed in pure organic solvents. In such cases, the selectivity of the reaction may depend on the organic solvent used. In non-aqueous solvents, hydrolytic enzymes catalyse the reverse reaction, ie the synthesis of esters and amides. The problem here is the low activity (catalytic power) of many hydrolases in organic solvents, and the unpredictable effects of the amount of water and type of solvent on the rate and selectivity. 

The previous chapters taught us how to ask questions about specific enzymatic reactions. In this chapter we will attempt to look for general trends in enzyme catalysis. In doing so we will examine various working hypotheses that attribute the catalytic power of enzymes to different factors. We will try to demonstrate that computer simulation approaches are extremely useful in such examinations, as they offer a way to dissect the total catalytic effect into its individual contributions. 

With the characterized mechanism, the next key question is the origin of its catalytic power. A prerequisite for this investigation is to reliably compute free energy barriers for both enzyme and solution reactions. By employing on-the-fly Born-Oppenheimer molecular dynamics simulations with the ab initio QM/MM approach and the umbrella sampling method, we have determined free energy profiles for the methyl-transfer reaction catalyzed by the histone lysine methyltransferase SET7/9... 

Enzymes have several remarkable catalytic properties such as high catalytic power and high selectivities under mild reaction conditions, as compared with those of chemical catalysts. In the field of organic synthesis, enzymes have often been employed as catalyst functional organic compounds were synthesized by the enzymatic selective reactions [1-5]. 

Enzymes are remarkable molecular devices that determine the pattern of chemical transformations in biological systems. The most striking characteristics of enzymes are their catalytic power and specificity. As a class of macromolecules, they are highly effective in catalyzing diverse chemical reactions because of their ability to specifically bind to a substrate and their ability to accelerate reactions by several orders of magnitude. Applying enzymes or organisms in... 

Immobilized enzymes are attached to a solid support by adsorption or chemical binding or mechanical entrapment in the pores of a gel structure but retain their catalytic power. Their merit is ease of separation from the finished reaction product. 

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