Monitoring the Role of Oxalate in Manganese Peroxidase

详细信息    查看全文

• 作者：Lucia Banci ; Ivano Bertini ; Lorenzo Dal Pozzo ; Rebecca Del Conte ; and Ming Tien
• 刊名：Biochemistry
• 出版年：1998
• 出版时间：June 23, 1998
• 年：1998
• 卷：37
• 期：25
• 页码：9009 - 9015
• 全文大小：155K
• 年卷期：v.37,no.25(June 23, 1998)
• ISSN：1520-4995

文摘

The water proton relaxation rate measurements between 0.01 and 50MHz on water solutionscontaining the cyanide adduct of the manganese-depleted manganeseperoxidase (MnP-CN^-) andincreasing amounts of Mn²⁺ have been determined. Theproton relaxivity curves have shown evidenceof the formation of the protein/Mn²⁺ complex and havebeen analyzed in order to obtain spin Hamiltonianparameters and correlation times. Oxalate is shown not to alterthe above profiles. This suggests that noprotein-Mn²⁺-oxalate ternary complex is formed andthat oxalate does not remove Mn²⁺ from theprotein.On the basis of high-resolution ¹H NMR experiments, wepropose that Ce³⁺ and Gd³⁺ bind at themanganesesite, and, on the basis of the charge, we propose that they may mimicMn³⁺. The water proton relaxationrates of water solutions containing manganese-depletedMnP-CN^- and increasing amounts of Gd³⁺havebeen measured and analyzed. Oxalate is shown to remove thetrivalent metal ions. This suggests thattrivalent metal ions bind oxalate and diffuse away from the proteinpresumably as oxalate complexes.Implications for the enzymatic mechanism arediscussed.