Kcat/Km就可以用来确定酶的最适底物，同一个酶对不同底物的Kcat/Km最大可相差100万倍。 当利用蛋白质工程对酶进行改造时，不同突变型的Kcat/Km也是需要测定的参数，用来表征酶催化效率的变化情况。

In chemistry, the term " turnover number " has two distinct meanings. In enzymology, the turnover number (kcat) is defined as the limiting number of chemical conversions of substrate molecules per second that a single active site will execute for a given enzyme concentration [ET] for enzymes with two or more active sites. [1] .

其算法很简单，用Kcat值除以Km值即可，单位一般为s-1×M-1或s-1×mM-1，注意两者是1000倍的关系，如上例，其Kcat/Km=2.93/3.65=1.11s-1×mM-1=1110s-1×M-1。 度呈正比。 通常发表论文的Vmax单位为nkat×mg-1protein，表示每毫克纯化的蛋白有多少个nkat活力。 这里有必要弄清楚酶活力单位的意义，国际上有两种活力单位：IU和Kat，它们的意义分别为：

2022年6月13日 · This report demonstrates a step-by-step process to visualize the meaning of kcat / KM on the reaction free energy diagram. The reciprocal form of the expression of kcat / KM shows that kcat / KM is a harmonic sum of kinetic terms that correspond to the heights of the transition states relative to the free enzyme.

kcat是一个很好的参数去衡量一个酶的催化效率，kcat越高，就说明单位时间内酶转化的分子数就越多，即酶的催化效率越高。 当底物浓度很稀的时候 ( [S]远小于Km)，米氏方程可近似写成v= [E] [S] kcat / Km，即kcat/ Km是酶与底物反应堆表观二级速率常数 (apparent second-orderrate constant)，又称为专一性常数 (specificity constant)，可以从另一角度表现一个酶的催化效率和完美程度，以及酶的最佳底物。

Vmax取决于酶位点的数量（Et）和酶将底物转化为产物的速率（kcat）。 如果知道添加到检测中酶位点的浓度（Et），则可以使用上述模型拟合催化常数Kcat。 计算Kcat时，浓度单位相互抵消，因此Kcat以反时间单位表示。 其代表转换量-单位时间内每个酶位点转化为产物的底物分子数。 1.创建一张XY数据表。 将底物浓度输入X，将酶速度输入Y。 如果有几个实验条件，则将第一个放入A栏，第二个放入B栏，依此类推。 也可以选择Prism的样本数据：酶动力学-Michaelis …

Km和Ks Km是米氏常数，定义为Km= (k-1+k2)/k1，物理意义是反应速度达到Vm一半时的底物浓度。 Ks是酶与底物复合物的解离常数，定义为Ks=k-1/k1。

All you have to do is find the [Et]. This is basically the total "Moles" of the enzymes you have used. which comes out to be 10^-10. Then you find the kcat = Vm/ [Et], then find kcat/km

If you know the concentration of enzyme sites you've added to the assay (E t) then you can calculate the catalytic constant K cat. It is defined to equal V max /E t. Vmax and the Y values (enzyme velocities) are expressed in units of concentration per time, and Et must be entered in those same concentration units.

Kcat and Km are both important parameters used to characterize enzyme kinetics. Kcat, also known as the turnover number, represents the maximum rate at which an enzyme can catalyze a reaction when it is fully saturated with substrate. On the other hand, Km, the Michaelis constant, is a measure of the affinity of an enzyme for its substrate.