催化常数(k_cat) or turnover number is the number of enzymatic reactions a single saturated enzyme molecule can catalyze per unit of time, usually expressed in s^-1. k_catis not dependent on the concentration of the enzyme, and is, therefore, a better parameter thanV_maxfor comparing different enzymes. Because k_catis the maximum number of chemical reactions a single enzyme molecule can catalyze, the maximum velocity (V_max) at a specific enzyme concentration is obtained by multiplying k_catwith the concentration of the enzyme ([E]), i.e., V_max= k_cat• [E]. This means, that if V_maxand [E], which can be experimentally measured, are known, k_catcan be calculated as follows [1].

k_cat= V_max/[E]

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.

V_max

Theory overview