Chu A H, Williams T J
Arch Biochem Biophys. 1984 Oct;234(1):129-37. doi: 10.1016/0003-9861(84)90333-3.
The effects of human serum albumin (HSA) on the rate of dithionite reduction of iron(III)deuteroporphyrin (iron(III)Dp) have been investigated in order to further characterize the porphyrin binding site and the changes manifested in this site under various conditions. These studies were performed under pseudo-first-order conditions, and in the presence of carbon monoxide as a "trapping agent" for the reduced iron(II)porphyrin. The rate of reduction of the free iron(III)Dp in phosphate buffer at pH 7.4 follows second-order kinetics with a rate constant (4.2 X 10(9) M-1 s-1) suggestive of a diffusion-controlled process. A six-orders of magnitude decrease in the rate of reduction was observed with iron(III)Dp was complexed with HSA. This result is consistent with HSA-bound porphyrin being less accessible to the aqueous environment. Additional studies demonstrated that both pH and anions induce various alterations in the complex that are reflected in the rate of reduction of iron(III)porphyrin.
为了进一步表征卟啉结合位点以及该位点在各种条件下所表现出的变化，研究了人血清白蛋白（HSA）对连二亚硫酸盐还原铁（III）氘代卟啉（铁（III）Dp）速率的影响。这些研究是在准一级条件下进行的，并且在一氧化碳作为还原铁（II）卟啉的“捕获剂”存在的情况下进行。在pH 7.4的磷酸盐缓冲液中，游离铁（III）Dp的还原速率遵循二级动力学，速率常数（4.2×10⁹ M⁻¹ s⁻¹）表明这是一个扩散控制过程。当铁（III）Dp与HSA络合时，观察到还原速率下降了六个数量级。该结果与HSA结合的卟啉在水性环境中较难接近一致。额外的研究表明，pH和阴离子都会引起络合物的各种变化，这反映在铁（III）卟啉的还原速率上。
