Enzymes conformational change

In 1958 Sarda and Desnuelle [79] discovered the lipase activation at the interfaces. They observed that porcine pancreatic lipase in aqueous solution was activated some 10-fold at hydrophobic interfaces which were created by poorly water-soluble substrates. An artificial interface created in the presence of organic solvent can also increase the activity of the lipase. This interfacial activation was hypothesized to be due to a dehydration of the ester substrate at the interface [80], or enzyme conformational change resulting from the adsorption of the lipase onto a hydrophobic interface [42,81,82]. 

W. Versees, J. Barlow, and J. Steyaert, Transition-state complex of the purine-specific nucleoside hydroalse of Trypanosoma vivax Enzyme conformational changes and implications on catalysis, J. Mol. Biol., 359 (2006) 331-346. 

Traditional steady-state kinetic studies rely on indirect observation of catalysis by monitoring the accumulation of product or consumption of substrate as a consequence of many reaction cycles with a trace of catalyst. Conclusions are limited to inference of the possible pathways for the order of addition of multiple substrates and release of products and quantification of two bulk kinetic parameters, kcat and kcaJKm- The parameter kcat defines the maximum rate of conversion of enzyme-bound substrate to product released into solution, but it cannot be used to establish whether the maximum rate of reaction is limited by enzyme conformational changes, rates of chemical reaction, or rates of product release per se it does, however, set a lower... 

Figure 1 Mechanism of DNA polymerization, (a) The structure of T7 DNA polymerase in a complex with DNA and an incoming nucleotide is shown with a fluorescent label attached to C514. Changes in the fluorescence allow quantification of the nucleotide-induced change in structure and its role in selectivity. Residues 233-411 and 436-454 have been removed to reveal the active site. Shown also are the O-helix and key catalytic residues From PDB 1 T7P (17). (b) The time dependence of the fluorescence change induced by nucleotide binding is shown at three concentrations of dCTP. The inset shows the measurement of the rate of dCTP dissociation from the E.DNAdd-dNTP complex. Analysis of these data defined the role of enzyme conformational changes in nucleotide selectivity. Both figures are reproduced with permission from Reference 6.

A separation step may not always be necessary when measuring low molecular weight haptens by EIA. In some cases, antibody binding to the enzyme-labeled hapten causes complete inhibition of enzyme activity. This may occur when antibody binding either sterically hinders substrate access to the active site of the enzyme or induces enzyme conformational changes. Whatever the cause, a more convenient homogeneous EIA system can result. - ... 

The cAMP-phosphodiesterase reaction would seem to conform to West-heimer s (1980) postulate (see p. 213), since large-scale enzyme conformational change would probably accompany any pseudorotatory process. Additionally, the cAMP-phosphodiesterase reaction does not conform to the corollary, since little mechanistic advantage is imputed in Eckstein s multiple-step pseudorotation mechanism—unless, of course, there is signifi-... 

ENZYME CONFORMATIONAL CHANGES AND FLUCTUATIONS EFFICIENT SAMPLING IN QM/MM SIMULATIONS... 

Curvature in an Eyring Plot is Used as Evidence for an Enzyme Conformational Change in the Catalysis of the Cleavage of the Co-C Bond of Vitamin... 

Curvature in an Eyring Plot is Used as Evidence for an Enzyme Conformational Change in the Catalysis of the Cleavage of the Co-C Bond of Vitamin B,2 371 Where TST May be Insufficient 374 The Transi tion States for S, 1 Reactions 377 Comparing Reactivity to Selectivity in Free Radical Halogenation 378... 

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