EC - Sirohydrochlorin cobaltochelatase

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IntEnz Enzyme Nomenclature


Accepted name:
sirohydrochlorin cobaltochelatase
Other names:
anaerobic cobalt chelatase
cobaltochelatase [ambiguous]
sirohydrochlorin cobalt-lyase [incorrect]
Systematic name:
cobalt-sirohydrochlorin cobalt-lyase (sirohydrochlorin-forming)



This enzyme is a type II chelatase, being either a monomer (CbiX) or a homodimer (CibK) and being ATP-independent. CbiK from Salmonella enterica uses precorrin-2 as the substrate to yield cobalt-precorrin-2. The enzyme contains two histidines at the active site that are thought to be involved in the deprotonation of the tetrapyrrole substrate as well as in metal binding. CbiX from Bacillus megaterium inserts cobalt at the level of sirohydrochlorin (factor-II) rather than precorrin-2.

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , DIAGRAM , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
Gene Ontology: GO:0016852
UniProtKB/Swiss-Prot: (25) [show] [UniProt]


  1. Schubert, H.L., Raux, E., Wilson, K.S. and Warren, M.J.
    Common chelatase design in the branched tetrapyrrole pathways of heme and anaerobic cobalamin synthesis.
    Biochemistry 38: 10660-10669 (1999). [PMID: 10451360]
  2. Brindley, A.A., Raux E., Leech, H.K., Schubert, H.L. and Warren, M.J.
    A story of chelatase evolution: Identification and characterisation of a small 13-15 kDa 'ancestral' cobaltochelatase (CbiXS) in the Archaea.
    J. Biol. Chem. 278: 22388-22395 (2003). [PMID: 12686546]
  3. Warren, M.J., Raux, E., Schubert, H.L. and Escalante-Semerena, J.C.
    The biosynthesis of adenosylcobalamin (vitamin B12).
    Nat. Prod. Rep. 19: 390-412 (2002). [PMID: 12195810]

[EC created 2004]