scholarly journals Sacrificial Cobalt–Carbon Bond Homolysis in Coenzyme B12 as a Cofactor Conservation Strategy

2018 ◽  
Vol 140 (41) ◽  
pp. 13205-13208 ◽  
Author(s):  
Gregory C. Campanello ◽  
Markus Ruetz ◽  
Greg J. Dodge ◽  
Harsha Gouda ◽  
Aditi Gupta ◽  
...  
Keyword(s):  
Conservation Strategy ◽  
Coenzyme B12 ◽  
Carbon Bond ◽  
Bond Homolysis

Unique carbon–carbon bond homolysis in 3-alkylcyclohexa-1,4-dienyl-3-carboxylic acid radicals

1996 ◽  
pp. 2199-2200 ◽  
Author(s):  
Paul A. Baguley ◽  
Gavin Binmore ◽  
Aynsley Milne ◽  
John C. Walton
Keyword(s):  
Carboxylic Acid ◽  
Carbon Bond ◽  
Carbon Carbon Bond ◽  
Bond Homolysis

A study of the cage mechanism for the homolytic cleavage of the cobalt-carbon bond in coenzyme B12 by varying the solvent viscosity

1991 ◽  
Vol 190 (1) ◽  
pp. 47-53 ◽  
Author(s):  
Leonard E.H. Gerards ◽  
Huibert Bulthuis ◽  
Martinus W.G. de Bolster ◽  
Sijbe Balt
Keyword(s):  
Coenzyme B12 ◽  
Homolytic Cleavage ◽  
Carbon Bond ◽  
Solvent Viscosity

Protein–coenzyme interactions in adenosylcobalamin-dependent glutamate mutase

2001 ◽  
Vol 355 (1) ◽  
pp. 131-137 ◽  
Author(s):  
Marja S. HUHTA ◽  
Hao-Ping CHEN ◽  
Craig HEMANN ◽  
C. Russ HILLE ◽  
E. Neil G. MARSH
Keyword(s):  
Gel Filtration ◽  
Visible Spectrum ◽  
Titration Calorimetry ◽  
Coenzyme B12 ◽  
Glutamate Mutase ◽  
Carbon Bond ◽  
Coenzyme Binding ◽  
Radical Intermediates ◽  
Bond Stretching ◽  
Uv Visible

Glutamate mutase catalyses an unusual isomerization involving free-radical intermediates that are generated by homolysis of the cobalt–carbon bond of the coenzyme adenosylcobalamin (coenzyme B12). A variety of techniques have been used to examine the interaction between the protein and adenosylcobalamin, and between the protein and the products of coenzyme homolysis, cob(II)alamin and 5′-deoxyadenosine. These include equilibrium gel filtration, isothermal titration calorimetry, and resonance Raman, UV-visible and EPR spectroscopies. The thermodynamics of adenosylcobalamin binding to the protein have been examined and appear to be entirely entropy-driven, with ∆S = 109 Jċmol-1ċK-1. The cobalt–carbon bond stretching frequency is unchanged upon coenzyme binding to the protein, arguing against a ground-state destabilization of the cobalt–carbon bond of adenosylcobalamin by the protein. However, reconstitution of the enzyme with cob(II)alamin and 5′-deoxyadenosine, the two stable intermediates formed subsequent to homolysis, results in the blue-shifting of two of the bands comprising the UV-visible spectrum of the corrin ring. The most plausible interpretation of this result is that an interaction between the protein, 5′-deoxyadenosine and cob(II)alamin introduces a distortion into the ring corrin that perturbs its electronic properties.

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