TY - JOUR
T1 - Redox Potentials of Cobalt Corrinoids with Axial Ligands Correlate with Heterolytic Co-C Bond Dissociation Energies
AU - Morita, Yoshitsugu
AU - Oohora, Koji
AU - Sawada, Akiyoshi
AU - Kamachi, Takashi
AU - Yoshizawa, Kazunari
AU - Hayashi, Takashi
N1 - Funding Information:
This work was supported by Grants-in-Aid for Scientific Research provided by JSPS KAKENHI Grant Numbers JP15H05804, JP24655051, JP15H00944, JP22105013, JP16H00837, the JSPS Japanese-German Graduate Externship, and JST PRESTO. Y.M. appreciates support from the JSPS Research Fellowship for Young Scientists (JSPS KAKENHI Grant Number JP14J00790).
PY - 2017/2/20
Y1 - 2017/2/20
N2 - We investigate the correlations between the redox potentials of nonalkylated cobalt corrinoids and the Co-C bond dissociation energies (BDEs) of the methylated species with an aqua or histidine axial ligand. A set of cobalt corrinoids, cobalamin, and its model systems, which include new version of myoglobin reconstituted with cobalt didehydrocorrin, are investigated. The Co(III)/Co(II) and Co(II)/Co(I) redox potentials of myoglobin reconstituted with cobalt tetradehydrocorrin and didehydrocorrin and the bare cofactors were determined. Density functional theory (DFT) calculations were performed to estimate the Co-C BDEs of the methylated species. It is found that the redox potentials correlate well with the heterolytic BDEs, which are dependent on the electronegativity of the corrinoid frameworks. The present study offers two important insights into our understanding of how enzymes promote the reactions: (i) homolysis is promoted by strong axial ligation and (ii) heterolysis is controlled by the redox potentials, which are regulated by the saturated framework and axial ligation in the enzyme.
AB - We investigate the correlations between the redox potentials of nonalkylated cobalt corrinoids and the Co-C bond dissociation energies (BDEs) of the methylated species with an aqua or histidine axial ligand. A set of cobalt corrinoids, cobalamin, and its model systems, which include new version of myoglobin reconstituted with cobalt didehydrocorrin, are investigated. The Co(III)/Co(II) and Co(II)/Co(I) redox potentials of myoglobin reconstituted with cobalt tetradehydrocorrin and didehydrocorrin and the bare cofactors were determined. Density functional theory (DFT) calculations were performed to estimate the Co-C BDEs of the methylated species. It is found that the redox potentials correlate well with the heterolytic BDEs, which are dependent on the electronegativity of the corrinoid frameworks. The present study offers two important insights into our understanding of how enzymes promote the reactions: (i) homolysis is promoted by strong axial ligation and (ii) heterolysis is controlled by the redox potentials, which are regulated by the saturated framework and axial ligation in the enzyme.
UR - http://www.scopus.com/inward/record.url?scp=85013392778&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85013392778&partnerID=8YFLogxK
U2 - 10.1021/acs.inorgchem.6b02482
DO - 10.1021/acs.inorgchem.6b02482
M3 - Article
C2 - 28165219
AN - SCOPUS:85013392778
VL - 56
SP - 1950
EP - 1955
JO - Inorganic Chemistry
JF - Inorganic Chemistry
SN - 0020-1669
IS - 4
ER -