Fenoll Lorena G, Rodríguez-López José Neptuno, García-Molina Francisco, García-Cánovas Francisco, Tudela José
GENZ: Grupo de Investigación Enzimología, Departamento de Bioquímica y Biología Molecular-A, Facultad de Biología, A. Correos 4201 Universidad de Murcia, Espinardo, E-30080 Murcia, Spain.
Int J Biochem Cell Biol. 2002 Apr;34(4):332-6. doi: 10.1016/s1357-2725(01)00133-9.
The complex reaction mechanism of tyrosinase involves three enzymatic forms, two overlapping catalytic cycles and a dead-end complex. Analytical expressions for the catalytic and Michaelis constants of tyrosinase towards phenols and oxygen were derived for both, monophenolase and diphenolase activities of the enzyme. Thus, the Michaelis constants of tyrosinase towards the oxygen (K(mO(2))) are related with the respective catalytic constants for monphenols (k(M)(cat)) and o-diphenols (k(D)(cat)), as well as with the rate constant, k(+8). We recently determined the experimental value of the rate constant for the binding of oxygen to deoxytyrosinase (k(+8)) by stopped-flow assays. In this paper, we calculate theoretical values of K(mO(2)) from the experimental values of catalytic constants and k(+8) towards several monophenols and o-diphenols. The reliability and the significance of the values of K(mO(2)) are discussed.
酪氨酸酶复杂的反应机制涉及三种酶形式、两个重叠的催化循环和一个终产物复合物。针对该酶的单酚酶和二酚酶活性，推导了酪氨酸酶对酚类和氧气的催化常数及米氏常数的解析表达式。因此，酪氨酸酶对氧气的米氏常数（K(mO(2))）与单酚（k(M)(cat)）和邻二酚（k(D)(cat)）各自的催化常数以及速率常数k(+8)相关。我们最近通过停流分析法测定了氧气与脱氧酪氨酸酶结合的速率常数（k(+8)）的实验值。在本文中，我们根据对几种单酚和邻二酚的催化常数及k(+8)的实验值计算了K(mO(2))的理论值，并讨论了K(mO(2))值的可靠性和意义。
