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The axial N-base has minor influence on Co-C bond cleavage in cobalamins

Jensen, Kasper LU and Ryde, Ulf LU (2002) In Journal of molecular structure. Theochem1981-01-01+01:002011-01-01+01:00 585(1). p.239-255
Abstract
We have investigated the properties of cobalamin complexes with imidazolate using the density functional B3LYP method, In particular, we have compared imidazolate (Imm) with imidazole and 5,6-dimethylbenzimidazole (DMB), and studied how constraints in the axial Co-N bond length may affect the strength of the Co-C bond. The results show that the optimum Co-N-Imm bond is similar to0.2 Angstrom shorter than that of imidazole. There is no indication from crystal structures that the histidine ligand would be deprotonated in the enzymes. However, it is likely that it attains some imidazolate character through its hydrogen bond to a conserved aspartate residue. The Co-N bond with imidazolate is three times more rigid than that with imidazole or... (More)
We have investigated the properties of cobalamin complexes with imidazolate using the density functional B3LYP method, In particular, we have compared imidazolate (Imm) with imidazole and 5,6-dimethylbenzimidazole (DMB), and studied how constraints in the axial Co-N bond length may affect the strength of the Co-C bond. The results show that the optimum Co-N-Imm bond is similar to0.2 Angstrom shorter than that of imidazole. There is no indication from crystal structures that the histidine ligand would be deprotonated in the enzymes. However, it is likely that it attains some imidazolate character through its hydrogen bond to a conserved aspartate residue. The Co-N bond with imidazolate is three times more rigid than that with imidazole or DMB, but twice as flexible as the Co-C bond. Constraints in the Co-N-Imm bond length give rise to a larger change in the corrin conformation than imidazole, but smaller than for DMB. The resulting effect for the Co-C bond dissociation energy is larger for imidazolate than for imidazole or DMB. However, even the largest reasonable distortion can only enhance catalysis by 15 kJ mol(-1). Therefore, we conclude that, irrespective of the nature of the N-base, constraints in the axial Co-N bond lengths cannot be the main reason for the catalytic power of cobalamin enzymes. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
butterfly effect, mechanism, mechano-chemical trigger, coenzyme B-12, density functional theory, cobalamin, corrin, ligand triad
in
Journal of molecular structure. Theochem1981-01-01+01:002011-01-01+01:00
volume
585
issue
1
pages
239 - 255
publisher
Elsevier
external identifiers
  • wos:000176287600022
  • scopus:0037123803
ISSN
0166-1280
DOI
10.1016/S0166-1280(02)00049-0
language
English
LU publication?
yes
id
9500b9cf-8e24-45db-97e9-f114d263a383 (old id 334804)
date added to LUP
2007-10-24 15:51:17
date last changed
2017-11-30 16:17:05
@article{9500b9cf-8e24-45db-97e9-f114d263a383,
  abstract     = {We have investigated the properties of cobalamin complexes with imidazolate using the density functional B3LYP method, In particular, we have compared imidazolate (Imm) with imidazole and 5,6-dimethylbenzimidazole (DMB), and studied how constraints in the axial Co-N bond length may affect the strength of the Co-C bond. The results show that the optimum Co-N-Imm bond is similar to0.2 Angstrom shorter than that of imidazole. There is no indication from crystal structures that the histidine ligand would be deprotonated in the enzymes. However, it is likely that it attains some imidazolate character through its hydrogen bond to a conserved aspartate residue. The Co-N bond with imidazolate is three times more rigid than that with imidazole or DMB, but twice as flexible as the Co-C bond. Constraints in the Co-N-Imm bond length give rise to a larger change in the corrin conformation than imidazole, but smaller than for DMB. The resulting effect for the Co-C bond dissociation energy is larger for imidazolate than for imidazole or DMB. However, even the largest reasonable distortion can only enhance catalysis by 15 kJ mol(-1). Therefore, we conclude that, irrespective of the nature of the N-base, constraints in the axial Co-N bond lengths cannot be the main reason for the catalytic power of cobalamin enzymes.},
  author       = {Jensen, Kasper and Ryde, Ulf},
  issn         = {0166-1280},
  keyword      = {butterfly effect,mechanism,mechano-chemical trigger,coenzyme B-12,density functional theory,cobalamin,corrin,ligand triad},
  language     = {eng},
  number       = {1},
  pages        = {239--255},
  publisher    = {Elsevier},
  series       = {Journal of molecular structure. Theochem1981-01-01+01:002011-01-01+01:00},
  title        = {The axial N-base has minor influence on Co-C bond cleavage in cobalamins},
  url          = {http://dx.doi.org/10.1016/S0166-1280(02)00049-0},
  volume       = {585},
  year         = {2002},
}