维生素C对酪氨酸酶催化反应的影响

目的通过观测 2 羧基 2 ,3 二羟基 5 ,6 醌 (多巴红 )的形成得到动力学测量结果 ,研究在酪氨酸酶与 3,4 二羟基 L 苯丙氨酸 (L DOPA)反应中维生素C(Vc)所起的作用。方法在酪氨酸酶催化氧化左旋多巴反应体系中加入Vc,在一定的时间间隔内测定多巴红的吸收度得到最初的曲线。对吸收度数据进行非线性的最小二乘方拟合得到有关动力学数据 ,就Vc在酪氨酸酶催化L DOPA反应中的作用提出反应机理。结果在Vc作用下酪氨酸酶氧化L DOPA的反应出现滞后现象 ,滞后时间与Vc的量成正比。结论Vc在催化反应中起着还原剂的作用

The effect of vitamin C on tyrosinase catalytic reaction

PurposeKinetic measurements were made by observing the fomation of the 2 carboxy 2,3 dihydroinol 5 6 quinone(dopachrome).The effect of vitamin C in the range 0.25～0.45mmol/L on the reactivity of tyrosinase with 3,4 dihydroxy L phenylslsnine( L dopa) was studied. MethodsTyrosinase was added to a reaction mixture containing both the L dopa and Vc. The initial curve portion was takenas a measure of the dopachrome absorbances at fix time intervals indicated. The kinetic data were calculated from the absorbances by a nonlinear Least Spuares.The mechanism for L dopa catalyzed by tyrosinase in the presence of Vc was proposed. ResultsThe time curve of tyrosinase catalytic reaction has lay period when Vc is added to the system of reation ,lay time is directly proportional to Vc comcentration.ConclusionThe experiment demonstrates that Vc is a reductant in reaction of tyrosinase catalytic L dopa.