Kinetic and Thermodynamic Analysis of the Specificity Constants

It can be readily shown that the specificity constant ksp = kcat/KM can be taken to act as a (pseudo) second-order rate constant in the rate equation for an enzymatic reaction that follows minimal Michaelis-Menten kinetics  

It should be emphasized that Equation 11 and Equation 12 represent identical rates as a result of the purely neutral substitutions ksp = / and cE = cEo/(l + cs/KM). Based on the format of Equation 12, it is rather tempting to treat the specificity 

P resolution type, where chirality occurs in the first substrate to enter and the product to leave the cycle. Similar profiles can be drawn for the reaction of the S-enantiomer and the deacylation reaction, F + — Q + E. 

Since the enantiomeric ratio is defined as the ratio of the specificity constants for the two enantiomers, one has (Equation 17)  

At this point, it is instructive to notice that the numerical example given above for the minimal Michaelis-Menten scheme will probably be very relevant to the situation for the majority of the enzymes considered so far. In consequence, it appears that the effects of organic solvents on the enantioselectivity are not restricted to their relative effects on the ground state system and the transition state. Instead, substantial contributions from the diffusional process parameters have to be taken into account as well. Since these contributions are probably better described by the Einstein-Smoluchovski relation, 

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