Mechanism
MUT reaction mechanism begins with homolytic cleavage of AdoB12's C-Co(III) bond, the C and Co atoms each acquire one of the electrons that formed the cleaved electron pair bond. The Co ion, therefore, fluctuates between its Co(III) and Co(II) oxidation states . Hence, the role of coenzyme B-12 in the catalytic process is that of a reversible free radical generator. The C-Co(III) bond is well suited to this function because it is inherently weak (dissociation energy = 109 kJ/mol) and appears to be further weakened through steric interactions with the enzyme. A homolytic cleavage reaction is unusual in biology; most other biological bond cleavage reactions occur via heterolytic cleavage (in which the electron pair forming the cleaved bond is fully acquired by one of the separating atoms).
Read more about this topic: Methylmalonyl-Co A Mutase
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