Influence of Cu(II) on the interaction between sulfite and horseradish peroxidase in vitro

Abstract: This paper discussed the quantitative influence of Cu(II) on the interaction between horseradish peroxidase (HRP) and sulfite (SO3 2−), which is a derivate of sulfite dioxide in human bodies, by using fluorescence spectrum and ultraviolet (UV) absorption spectrometry in vitro. The results show that under the conditions of physiological pH and room-temperature, Cu(II) can bind strongly with both the protein part and the ferroporphyrin part in HRP at a low concentration (10−4 molL−1), and the combination constants are 2.047×103 and 7.66×102 Lmol−1, respectively. Under the same conditions, SO3 2− at low concentrations (<0.15molL−1) has little quenching for the fluorescence of HRP at 330nm, and the combination constant is 0.108Lmol−1. While the fluorescence intensity at 440nm enhance gradually with the increased concentration of SO3 2− (<0.1molL−1), and the combination constant is 8.219Lmol−1. These indicate that SO3 2− at low concentration has little reaction with the enzyme protein part in HRP but obvious reaction with the ferroporphyrin part in HRP. After SO3 2− at low concentrations is added into the HRP-Cu(II) binary system, the reaction constants between SO3 2− and the enzyme protein part in HRP increase rapidly. Compared with the absence of Cu(II), the combination constant of SO3 2− with the enzyme protein part in HRP increases nearly 70 times with a certain Cu(II) concentration (5.0×10−4 molL−1) in the system. However, the presence of Cu(II) in the system has little effect on the reaction constants between SO3 2− and the ferroporphyrin part in HRP. [Copyright &y& Elsevier]