Functional Model of Vitamin B12 and F430-dependent Enzymes

2014 Fiscal Year Final Research Report

• Project/Area Number: 24655051
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Inorganic chemistry
• Research Institution: Osaka University
• Principal Investigator: HAYASHI Takashi 大阪大学, 工学(系)研究科(研究院), 教授 (20222226)
• Co-Investigator(Renkei-kenkyūsha): OOHORA Koji 大阪大学, 大学院工学研究科, 助教 (10631202)
• Research Collaborator: MORITA Yoshitsugu
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: メチオニン合成酵素 / ミオグロビン / コバルトコリン / メチル基転移 / 酵素モデル

Outline of Final Research Achievements

Methionine synthase is responsible for the methylation of homocystein to yield methionine. Our group has recently prepared an enzyme model using a unique conjugate between apomyoglobin and a cobalt tetradehydrocorrin complex. The Co(II) tetradehydrocorrin complex as an artificial cofactor is inserted into the heme pocket of apomyoglobin with axial ligation of His93, which is characterized by EPR spectroscopy and X-ray crystal structure analysis. Reduction of the protein upon addition of dithionite is found to provide a Co(I) complex. The crystal structure of the Co(I) complex in the protein clearly reveals the tetra-coordinate species which forms due to the cleavage of the axial ligation. This behavior has been proposed to occur during formation of cob(I)alamin as a reaction intermediate. The addition of methyl iodide to the Co(I) species provides a photoactive species and the ESI-TOF MS spectrum of the species supports the formation of a Co-CH3 bond in the heme pocket.

Free Research Field

生物無機化学