Cobalt chelatase

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cobalt chelatase
EVWong CC2XVX raytraced.png
Putative cobalt chelatase monomer from Desulvobrio vulgaris.[1]
EC number
CAS number 81295-49-0
IntEnz IntEnz view
ExPASy NiceZyme view
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / EGO
Cobalt chelatase, CobT subunit
Symbol CobT
Pfam PF06213
InterPro IPR006538

Cobalt chelatase (EC is an enzyme that catalyzes the chemical reaction

ATP + hydrogenobyrinic acid a,c-diamide + Co2+ + H2O ADP + phosphate + cob(II)yrinic acid a,c-diamide + H+

The 4 substrates of this enzyme are ATP, hydrogenobyrinic acid a,c-diamide, Co2+, and H2O, whereas its 4 products are ADP, phosphate, cob(II)yrinic acid a,c-diamide, and H+.

The aerobic cobalt chelatase (aerobic cobalamin biosynthesis pathway)[2][3] consists of three subunits, CobT, CobN (InterPro: IPR003672) and CobS (InterPro: IPR006537).

Cobalamin (vitamin B12) can be complexed with metal via the ATP-dependent reactions (aerobic pathway) (e.g., in Pseudomonas denitrificans) or via ATP-independent reactions (anaerobic pathway) (e.g., in Salmonella typhimurium).[4][5] The corresponding cobalt chelatases are not homologous. However, aerobic cobalt chelatase subunits CobN and CobS are homologous to Mg-chelatase subunits BchH and BchI, respectively.[5] CobT, too, has been found to be remotely related to the third subunit of Mg-chelatase, BchD (involved in bacteriochlorophyll synthesis, e.g., in Rhodobacter capsulatus).[5]

This enzyme belongs to the family of ligases, specifically those forming nitrogen-D-metal bonds in coordination complexes. The systematic name of this enzyme class is hydrogenobyrinic-acid-a,c-diamide:cobalt cobalt-ligase (ADP-forming). Other names in common use include hydrogenobyrinic acid a,c-diamide cobaltochelatase, CobNST, and CobNCobST. This enzyme participates in porphyrin and chlorophyll metabolism.


  1. ^ Romao CV, Ladakis D, Lobo SAL, Carrondo MA, Brindley AA, Deery E, Matias PM, Pickersgill RW, Saravia LM, Warren MJ. Evolution in a family of chelatases facilitated by the introduction of active site asymmetry and protein oligomerization. (2011) Proc. Natl. Acad. Sci. USA. 108, 97-102. Image drawn in PyMOL.
  2. ^ Crouzet J, Cameron B, Cauchois L, Rigault S, Blanche F, Guilhot C, Levy-schil S, Rouyez MC (1991). "Genetic and sequence analyses of a Pseudomonas denitrificans DNA fragment containing two cob genes". J. Bacteriol. 173 (19): 6058–6065. PMC 208352Freely accessible. PMID 1917840. 
  3. ^ Crouzet J, Cameron B, Blanche F, Thibaut D, Debussche L, Couder M (1992). "Assay, purification, and characterization of cobaltochelatase, a unique complex enzyme catalyzing cobalt insertion in hydrogenobyrinic acid a,c-diamide during coenzyme B12 biosynthesis in Pseudomonas denitrificans". J. Bacteriol. 174 (22): 7445–7451. PMC 207441Freely accessible. PMID 1429466. 
  4. ^ Roth JR, Lawrence JG, Bobik TA (1996). "Cobalamin (coenzyme B12): synthesis and biological significance". Annu. Rev. Microbiol. 50: 137–181. PMID 8905078. doi:10.1146/annurev.micro.50.1.137. 
  5. ^ a b c Willows RD, Al-Karadaghi S, Hansson M, Fodje MN, Hansson A, Olsen JG, Gough S (2001). "Interplay between an AAA module and an integrin I domain may regulate the function of magnesium chelatase". J. Mol. Biol. 311 (1): 111–122. PMID 11469861. doi:10.1006/jmbi.2001.4834. 

Further reading[edit]

This article incorporates text from the public domain Pfam and InterPro IPR006538