# Vmax

In accordance with the Michaelis-Menten equation, the initial reaction rate (V0) increases at increased substrate concentrations ([S]). The reaction rate increases more at lower substrate concentrations, and it eventually reaches a plateau, approaching the maximum velocity (Vmax) (Fig. 1). The maximum initial velocity is reached when the enzyme is saturated, when enough substrate is present to ensure that practically all the enzyme is part of the enzyme-substrate complex. Because the enzyme can never be completely saturated, Vmax is never fully reached. Vmax is dependent on 2 things: the turnover number of the enzyme (kcat), and the concentration of the enzyme ([E]) [1]. V max is never fully reached. V max is dependent on two things: the turnover number or k cat of the enzyme, and the concentration of the enzyme.

Vmax = [E] • kcat V max is equal to the enzyme concentration times the k cat

Thus, a higher [E] leads to a higher Vmax. enzyme concentration leads to a higher V max. The turnover number will be described in more detail on the following page.

Figure 1: An illustration of the Lineweaver-Burk equation fitted to a double-reciprocal transformation of an enzyme kinetic dataset.

## Determining Vmax V max

Just like km, Vmax k m, V max can be determined using the Lineweaver-Burk equation (Figure 1):

1/V0 = 1/Vmax + Km/Vmax • 1/[S] the reciprocal of V 0 is equal to the reciprocal of V max plus K m divided by V max times the reciprocal of the substrate's concentration

Based on this equation, a straight line fitted to a double reciprocal plot will have the y-intercept 1/Vmax, and Vmax can therefore be obtained by taking the reciprocal to this intercept [1]. the reciprocal of V max, and V max can therefore be obtained by taking the reciprocal to this intercept.

## References

1. Lehninger, Albert L.; Nelson, David L.; Cox, Michael M. (2008). Principles of Biochemistry (5th ed.). New York, NY: W.H. Freeman and Company. ISBN 978-0-7167-7108-1.

kcat

Theory overview