Can you rephrase the question? I am not very sure what you mean by biological system. Inefficient or hyperactive enzymes lead to metabolic disorders. Historically one would identify lack/lowered activity of a particular enzyme in disease conditions and compare it to the normal (wild type) enzyme. Later DNA sequencing came about and then it was easy to identify the mutation and correlate it with function (Km and kcat). Structural biology later aided in the precise chemical underpinning of structure and function. 

For many metabolic enzymes bacterial complementation systems are available and growth curves can be plotted in defined media that will roughly reflect enzyme efficiency(Kcat/Km). You can do this by transfecting eukaryotic cells  with appropriate plasmids and careful control experiments.

Hope this will help.  

To begin with, you can ask whether the rate of an enzyme-catalyzed reaction in vivo is controlled by substrate concentration. If the Km for the substrate is similar to the in vivo concentration of that substrate, then the rate of product formation will vary as the substrate concentration varies. In contrast, if the Km is much lower then the substrate concentration, then the rate of product formation will be maximal and will not vary unless the substrate concentration drops dramatically. (This does not take into account allosteric regulation of the enzyme activity, or the fact that many enzymes are multi-substrate.)

Second, if you know the kcat, the in vivo enzyme concentration, the substrate concentration and the Km, you can calculate the rate of product formation. This will tell you whether the product concentration in vivo is limited by the amount of enzyme present.

This is an idealized way of looking at it. In reality, there may be multiple points of regulation of enzyme activity, including allosteric effectors, product inhibition, substrate tunneling in multi-enzyme complexes, and so forth.