Conformation Changing, in enzymes

The addition of 1 x 10 3 M acetyl glutamate to frog liver enzyme preparation causes a 10% and immediate increase in fluorescence. This effect has been confirmed by Edelhoch (8), who concurs in our interpretation that this finding signifies acetyl glutamate-induced conformational changes of carbamyl-P synthetase. We believe that the decrease in stability induced by substrates and cofactors is, whenever it is found to occur, the simplest and most sensitive method available for the detection and study of conformational changes in enzymic proteins. 

Solvent Type The affect of different organic solvents on various enzyme catalytic activities has been demonstrated (37). From a mechanistic standpoint, the effect of organic solvents on enzyme catalysis is still debated (38). Conformational changes in enzymes, when suspended in organic solvents, have been reported to result in alteration of substrate specificity and affinity of substrates for enzymes (39). The polarity of organic solvents affects lipase-catalyzed reactions as do other variables that are critical to enzyme activity in organic media. The nature of the... 

Since the coordinates log/Cf and log/<,- are independent of each other, a correlation between log/cf and log/ ,- as in Equation (29) would demonstrate the existence of a linear free energy relationship The demonstration of a linear free energy relationship by this means is not necessary for chemical systems because these usually involve substituent change directly adjacent to the reaction centre the correlation is thus chemically reasonable. Application of Equation (29) is significant when the substituent changes may not be so obviously connected with the reaction centre as in the case of the effect of point mutation on conformational changes in enzymes. 

Apart from the direct conformational changes in enzymes, which may occur at very high pressures, pressure affects enzymatic reaction rates in SCFs in two ways. First, the reaction rate constant changes with pressure according to transition stage theory and standard thermodynamics. Theoretically, one can predict the effect of pressure on reaction rate if the reaction mechanism, the activation volumes and the compressibility factors are known. Second, the reaction rates may change with the density of SCFs because physical parameters, such... 

B. Havsteen, Conformational Changes in Enzymes Accompanying Catalysis, University Press, Aarhus (1968). 

Yeast Alcohol Dehydrogenase. Conformational changes are known to play an important role in the mechanism of enzyme action. The existence of conformational changes in enzymes bound to coenzymes or substrates has been postulated by several investigators (Nozaki et al., 1957 Sekuzu et al., 1957 Yonetani and Theorell, 1962 DiSabato and Kaplan, 1964 DiSabato and Kaplan, 1965). Hvidt and her... 

An important outcome of this investigation was the realization that H-D exchange can be successfully employed to study subtle conformational changes in enzymes brought about by coenzymes. 

Certain serine, tyrosine or threonine residues in proteins can be phosphorylated by protein kinases and dephosphorylated by protein phosphatases (e.g. Chapters 25 and 27). This causes conformational changes in enzyme proteins which increase or decrease activity. This very important regulatory mechanism is confirmed since protein kinases and phosphatases amount to 5% of the proteins encoded by the human genome. Current research has shown that abnormalities of protein phosphoiylation are associated with diseases such as cancer, diabetes and inflammation, the protein kinases and phosphatases are therefore targets for future drug therapy... 

Structures.—Mechanisms of the activation and inhibition of enzymes by antibodies and the use of immunochemical methods for studying the structure of the active site, quaternary structure, and conformational changes in enzymes during the interaction with substrates and other ligands have been discussed. ... 

While the chemiosmotic hypothesis does not embrace the need for the mediation of a chemical coupling compound(s) or for conformational coupling interaction(s) between the redox system and the ATP-synthesizing system, Mitchell notes that there is every reason to believe that conformational interactions may be involved within the translocation system itself, in a manner consistent with the role of conformational changes in enzymic catalysis, as elaborated in Chapters 3 and 4 of this book. 

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