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6 Cards in this Set
- Front
- Back
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Macrocylic metallocofactors (4)
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Cobalamin (Co)
Tetrapyrroles (Ni) Porphyrins (Fe) Chlorophyll (Mg) |
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Metal clusters
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Fe-S (Fe4S4, Fe2)
FeMoCo Cu2, mixed metal clusters |
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Single metal sites
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Non-heme iron
Cu2+ mostly structural sites: Ca2+, Zn2+ |
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The Cobalamin cofactor
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- 3 States, most reduced is Cb(1)
- (1,3) are active, (2) is inactive - Vitamin B12 - Catalyzes three reaction types: - Intramolecular rearrangements - Reductions of ribonucleotides to deoxyribonucleotides (DNA synthesis) -Methyl group transfers (assisted by tetrahydrofolate) |
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General Mechanism for AdoCbl-Dependent Rearrangement Reactions
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C-Co bond to generate 5’-DA radical
The 5’DA radical mediates H abstraction from substrate to form the intermediate 5’-DA and substrate radical. |
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Summary: Two Roles of Cobalamins
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Adenosyl cobalamin = adenosyl radical
Methyl cobalamin = methyl donor |
