Kinetic parameters for tyrosinase-catalyzed reactions.

Here Km, Michaelis-Menten constant defines the affinity of the substrate for the enzyme; Vmax, the rate at which a substrate will be converted to product once bound to the enzyme; kcat the enzyme turnover, number of substrate molecules turned over per enzyme molecule per minute. It is defined to equal Vmax/Et, where Et is concentration of enzyme in µmol; kcat/Km, enzyme efficiency.其中Km为米氏常数（Michaelis-Menten constant），用于表征底物对酶的亲和力；Vmax为最大反应速率，即底物与酶结合后转化为产物的速率；kcat为催化常数（kcat），又称酶周转数，指每分钟每个酶分子所转化的底物分子数，其定义为Vmax与Et的比值，其中Et为酶的浓度（单位：µmol）；kcat/Km则为酶的催化效率。