Interdepartmental Laboratory of Electron Microscopy, University Roma Tre, Via della Vasca Navale 79, I-00146 Roma, Italy.
Biochem Biophys Res Commun. 2011 Mar 4;406(1):112-6. doi: 10.1016/j.bbrc.2011.02.005. Epub 2011 Feb 4.
Human serum heme-albumin (HSA-heme-Fe) displays globin-like properties. Here, kinetics of O(2)-mediated oxidation of ferrous nitrosylated HSA-heme-Fe (HSA-heme-Fe(II)-NO) is reported. Values of the first-order rate constants for O(2)-mediated oxidation of HSA-heme-Fe(II)-NO (i.e., for ferric HSA-heme-Fe formation) and for NO dissociation from HSA-heme-Fe(II)-NO (i.e., for NO replacement by CO) are k=9.8 × 10(-5) and 8.3 × 10(-4) s(-1), and h=1.3 × 10(-4) and 8.5 × 10(-4) s(-1), in the absence and presence of rifampicin, respectively, at pH=7.0 and T=20.0 °C. The coincidence of values of k and h indicates that NO dissociation represents the rate limiting step of O(2)-mediated oxidation of HSA-heme-Fe(II)-NO. Mixing HSA-heme-Fe(II)-NO with O(2) does not lead to the formation of the transient adduct(s), but leads to the final ferric HSA-heme-Fe derivative. These results reflect the fast O(2)-mediated oxidation of ferrous HSA-heme-Fe and highlight the role of drugs in modulating allosterically the heme-Fe-atom reactivity.
人血清血红素白蛋白（HSA-血红素-Fe）显示球蛋白样性质。本文报道了亚铁亚硝酰化 HSA-血红素-Fe（HSA-血红素-Fe(II)-NO）的 O2 介导氧化的动力学。O2 介导的 HSA-血红素-Fe(II)-NO（即形成三价 HSA-血红素-Fe）和 HSA-血红素-Fe(II)-NO 中 NO 解离（即 CO 取代 NO）的一级速率常数的值分别为 k=9.8×10(-5)和 8.3×10(-4) s(-1)，以及 h=1.3×10(-4)和 8.5×10(-4) s(-1)，在 pH=7.0 和 T=20.0°C 时分别存在和不存在利福平的情况下。k 和 h 的值一致表明，NO 解离代表 O2 介导的 HSA-血红素-Fe(II)-NO 氧化的限速步骤。将 HSA-血红素-Fe(II)-NO 与 O2 混合不会导致瞬态加合物的形成，而是导致最终的三价 HSA-血红素-Fe 衍生物的形成。这些结果反映了亚铁 HSA-血红素-Fe 的快速 O2 介导氧化，并强调了药物在变构调节血红素-Fe 原子反应性方面的作用。
