The Incorporation of Product Binding

A more realistic but still relatively simple model of enzyme catalysis includes binding of both substrate and product as described by Equation 11.9. This reaction is characterized by five individual rate constants k and k2, and k4 and k5, correspond to the forward and reverse binding steps of the substrate S and product P to the enzyme E, respectively, while k3 expresses the irreversible chemical conversion at the enzyme active site  

With both intermediates in steady-state, the rate of loss of substrate is equal to the rate of product formation. Also 

Rearrangement of Equation 11.14 and substitution into Equation 11.13 gives  

When initial rates (u ) are measured the concentration of product is negligible and 

Finally, introduction of the commonly used symbols Vmax and Km yields the Briggs-Haldane rate equation for enzymatic reactions (compare with Equation 11.6) 

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