Biological enzyme modeling catalytic power

Two distinct features of enzymes, high catalytic power and high specificity are reasonably and consistently explained by the rigid molecular anvil model. The flexible model similarly explains some general properties of enzymes such as showing maximum activity at the optimum values of environmental parameters such as pH, temperature, concentration of chemical substances. The relation between these fundamental properties of enzymes and biological phenomena is discussed. 

The techniques of molecular biology discussed in Chapter 6 have permitted detailed examination of the catalytic triad. In particular, site-directed mutagenesis has been used to test the contribution of individual amino acid residues to the catalytic power of an enzyme. Subtilisin has been extensively studied by this method. Each of the residues within the catalytic triad, consisting of aspartic acid 32, histidine 64, and serine 221, has been individually converted into alanine, and the ability of each mutant enzyme to cleave a model substrate has been examined (Figure 9.16). As expected, the conversion of active-site serine 221 into alanine dramatically reduced catalytic power the value of k fell to less than one-millionth of its value for the wild-type enzyme. The value of. Sf was essentially unchanged its increase by no more than a factor of two indicated that substrate binding is not significantly affected. The mutation of histidine 64 to alanine... 

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