Enzymatic catalysis first-order reactions

Figure 35. The distribution curve of enzymes with respect to the reaction rate constant (first-order) in enzymatic catalysis.

The decrease in substrate produced by enzymatic catalysis is exponential in nature and can be described by the first order chemical reactions (Equation 28). 

Catalysis or Catalytic Power is the ratio between the reaction rate of the catalyzed reaction and that of the uncatalyzed reaction. It is defined as kcat/feun where kcat is the rate of the catalyzed reaction and kun is the rate of the uncatalyzed reaction. By definition, catalysis should be unit-less (a ratio of rate constants), thus care must be practised while determining Catalytic Power that k at and k n have the same units. Alternatively, the second order uncatalyzed reaction s rate (M s units) can be divided by kcat (s ) and the ratio then has units of concentration (M). This concentration is called effective concentration [2] and could be addressed as the concentration of functional groups or substrates in the enzyme s active site. Since that effective concentration is often in the thousands of M range, it is not a physically meaningful concentration, but rather a manifestation of the role of correct orientation, dynamic, and other catalytic effects induced by the enzyme. A similar approach used the substrate concentration in which the enzymatic and uncatalyzed rates are equal as an indicator for catalytic power [8j. The advantage of the first... 

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