tailieunhanh - ENZYME KINETICS A MODERN APPROACH – PART 9

Michaelis-Menten hoặc mô hình động học hyperbolic, được sử dụng ở đây để minh họa một mô hình có thể được sử dụng để hướng dẫn giải thích và kết luận. Ức chế chất nền trong các nghiên cứu trên động học enzyme là một tài sản quan sát thường xuyên hơn có lẽ nhiều người sẽ dự đoán. | IS THERE CONSISTENCY WORKING WITHIN THE CONTEXT OF A KINETIC MODEL 185 Michaelis-Menten or hyperbolic kinetics model is used here to illustrate how a model can be employed to guide interpretations and conclusions. Substrate inhibition in studies on enzyme kinetics is a property observed more often than perhaps one would anticipate. An example of an enzyme reaction subject to substrate inhibition is illustrated in Fig. . A conclusion that may be reached upon the presentation of such data is . the enzyme reaction was subject to substrate inhibition at S of greater than 2 mM. This would be a naive comment a more a precise comment would be that . the enzyme reaction was subject to substrate inhibition and reaction rates started to decline at S of greater than 2 mM. The difference between these statements lies much deeper than simply semantics. To make an appropriate assessment of the pattern of inhibition one need only compare the pattern of reaction velocity versus S observed relative to the pattern predicted from an application of the hyperbolic kinetics model. This requires making an estimate of vmax and Km from the data available. Transforming the original data to a Lineweaver-Burke plot despite the aforementioned limitations indicates that only four data points at low S can be used to estimate vmax and Km as units and mM respectively Fig. . The predicted uninhibited behavior of the enzyme activity can now be calculated by applying the rectangular hyperbola Eq. yielding the upper curve in Fig. and it becomes clear that inhibition was obvious at S 1 mM. The degree of inhibition is expressed appropriately as the difference between observed and predicted activity at any S value if one makes interpretations within the context of the Michaelis - Menten model. Because of the leveling off of enzyme activity at 3 to 5 mM S Fig. another conclusion that may be reached through intuition is that . this pattern of activity can be explained by