The nitrite reductase activity of horse heart carboxymethylated-cytochrome c is modulated by cardiolipin

详细信息    查看全文

• 作者：Paolo Ascenzi ; Diego Sbardella…
• 刊名：Journal of Biological Inorganic Chemistry
• 出版年：2016
• 出版时间：June 2016
• 年：2016
• 卷：21
• 期：3
• 页码：421-432
• 全文大小：815 KB
• 刊物类别：Biomedical and Life Sciences
• 刊物主题：Life Sciences
  Biochemistry
  Microbiology
  
• 出版者：Springer Berlin / Heidelberg
• ISSN：1432-1327
• 卷排序：21

文摘

Horse heart carboxymethylated cytc (CM-cytc) displays myoglobin-like properties. Here, the effect of cardiolipin (CL) liposomes on the nitrite reductase activity of ferrous CM-cytc [CM-cytc-Fe(II)], in the presence of sodium dithionite, is reported between pH 5.5 and 7.6, at 20.0 °C. Cytc-Fe(II) displays a very low value of the apparent second-order rate constant for the NO₂−-mediated conversion of cytc-Fe(II) to cytc-Fe(II)-NO [k_on = (7.3 ± 0.7) × 10−2 M−1 s−1; at pH 7.4], whereas the value of k_on for NO₂− reduction by CM-cytc-Fe(II) is 1.1 ± 0.2 M−1 s−1 (at pH 7.4). CL facilitates the NO₂−-mediated nitrosylation of CM-cytc-Fe(II) in a dose-dependent manner, the value of k_on for the NO₂−-mediated conversion of CL–CM-cytc-Fe(II) to CL–CM-cytc-Fe(II)-NO (5.6 ± 0.6 M−1 s−1; at pH 7.4) being slightly higher than that for the NO₂−-mediated conversion of CL–cytc-Fe(II) to CL–cytc-Fe(II)-NO (2.6 ± 0.3 M−1 s−1; at pH 7.4). The apparent affinity of CL for CM-cytc-Fe(II) is essentially pH independent, the average value of B being (1.3 ± 0.3) × 10−6 M. In the absence and presence of CL liposomes, the nitrite reductase activity of CM-cytc-Fe(II) increases linearly on lowering pH and the values of the slope of the linear fittings of Log k_on versus pH are −1.05 ± 0.07 and −1.03 ± 0.03, respectively, reflecting the involvement of one proton for the formation of the transient ferric form, NO, and OH−. These results indicate that Met80 carboxymethylation and CL binding cooperate in the stabilization of the highly reactive heme-Fe atom of CL–CM-cytc.KeywordsHorse heart carboxymethylated-cytochrome cCardiolipin liposomesNitrite reductase activityKinetics