Examples of Enzyme-Catalyzed Reactions and Their Treatment

Examples of Enzyme-Catalyzed Reactions and Their Treatment 

It is not always immediately apparent from an enzymatic reaction whether it should be treated with single- or dual-substrate enzyme kinetic expressions. Lactose hydrolase, which catalyzes the hydrolysis of lactose according to 

Lactate dehydrogenase (misnamed since it usually functions in the reverse direction and so would be more aptly named pyruvate hydrogenase) represents a yet more complicated system  

In this case, the question is whether H+ should be considered a third substrate. It has, in fact, been treated in this manner by researchers, who have shown that if both pymvate and NADH concentrations are maintained at saturating levels, the initial rate of the enzymatic reaction is pH dependent, showing a Gaussian-like curve over the pH range 6-8. Data taken on the alkaline side of this curve may be used to obtain a KmU value, or, alternately, the alkaline pH value at Vm ix/2 value may be read 

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