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Volumn 127, Issue 25, 2005, Pages 9117-9128

How the Co-C bond is cleaved in coenzyme B12 enzymes: A theoretical study

Author keywords

[No Author keywords available]

Indexed keywords

CHEMICAL BONDS; DEFORMATION; DISSOCIATION; FREE RADICALS; ORGANOMETALLICS; QUANTUM THEORY; SUBSTRATES; VITAMINS;

EID: 21344463602     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja050744i     Document Type: Article
Times cited : (112)

References (99)
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    • 12 proteins; Kräutler, B., Arigoni, D., Golding, B. T., Eds.; Wiley-VCH: Weinheim, 1998; Chapter 25.
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    • Finke, R.G.1
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    • (1985) Science , vol.227 , pp. 869-875
    • Halpern, J.1
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    • 84855618590 scopus 로고    scopus 로고
    • Kräutler, B., Arigoni, D., Golding, B. T., Eds.; Wiley-VCH: Weinheim; Chapter 16
    • 12 proteins; Kräutler, B., Arigoni, D., Golding, B. T., Eds.; Wiley-VCH: Weinheim, 1998; Chapter 16.
    • (1998) 12 Proteins
    • Marsh, E.N.G.1    Holloway, D.E.2    Chen, H.P.3
  • 67
    • 84855618590 scopus 로고    scopus 로고
    • Kräutler, B., Arigoni, D., Golding, B. T., Eds.; Wiley-VCH; Weinheim; Chapter 16
    • 12 proteins; Kräutler, B., Arigoni, D., Golding, B. T., Eds.; Wiley-VCH; Weinheim, 1998; Chapter 16
    • (1998) 12 Proteins
    • Marsh, E.N.G.1    Holloway, D.E.2    Chen, H.-P.3
  • 71
    • 0003845334 scopus 로고    scopus 로고
    • Karlsruhe University, Department Theoretical Chemistry
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    • (2001) Turbomole, Version 5.6
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    • note
    • It should be noted that the experimental BDE of MeCbl is 155 ± 13 kJ/mol, in good agreement with our theoretical estimate (160 kJ/mol). However, our estimate of the BDE in CoCorImAdo, 143 kJ/mol, is quite different from that of AdoCbl, 126 ± 8 kJ/mol. This difference cannot be attributed to the change of the axial ligand from Im to 5,6-dimethyl-benzimidazole, which is actually predicted to increase the BDE, but only by 1 kJ/mol. This discrepancy remains to be explained, but it is possible that the Ado radical does not fully dissociate from the corrin ring in the experiment (cage effects), so that what is actually measured for AdoCbl is only the dissociation curve to a finite distance (∼4 Å), as is shown in Figure 3, explaining the difference between MeCbl and AdoCbl. This is supported by the fact that the Co-C bond distances in the two coenzymes are almost the same (within 0-0.05 Å), both in calculations and experiments, although a linear relation has been established between the Co-C bond length and the BDE. In the following discussions, we will ignore this discrepancy between experiments and calculations and use our calculated values, to make the discussion more clear.
  • 86
    • 21344463722 scopus 로고    scopus 로고
    • note
    • III state can be strongly destabilized although it is not reflected in a long Co-C bond.
  • 87
    • 21344443011 scopus 로고    scopus 로고
    • note
    • II state by CoCorImAdo itself (i.e. hydrogen bonds within the QM system, but it includes the stabilization by the Cor side chains, which are not in the quantum system).
  • 88
    • 21344436768 scopus 로고    scopus 로고
    • note
    • IIICorAdo as the reference state, the strain energy is 296 kJ/mol, the difference being the BDE.
  • 89
  • 98
    • 21344434024 scopus 로고    scopus 로고
    • note
    • In fact, 99 kJ/mol is larger than the geometry contribution in Table 3, 57 kJ/mol, because the mutants were only run with system 2 fixed, to make the calculations faster and more stable.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.