Cobalt chelatase

Cobalt chelatase (EC 6.6.1.2) is an enzyme that catalyzes the chemical reaction

ATP + hydrogenobyrinic acid a,c-diamide + Co²⁺ + H₂O ${\displaystyle \rightleftharpoons }$ ADP + phosphate + cob(II)yrinic acid a,c-diamide + H⁺

cobalt chelatase
Putative cobalt chelatase monomer from Desulvobrio vulgaris.[1]
Identifiers
EC number	6.6.1.2
CAS number	81295-49-0
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Gene Ontology	AmiGO / QuickGO
Search PMC articles PubMed articles NCBI proteins

The four substrates of this enzyme are ATP, hydrogenobyrinic acid a,c-diamide, Co²⁺, and H₂O; its four 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).

The macrocycle of vitamin B12 can be complexed with metal via the ATP-dependent reactions in the aerobic pathway (e.g., in Pseudomonas denitrificans) or via ATP-independent reactions of sirohydrochlorin in the 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 is part of the biosynthetic pathway to cobalamin (vitamin B₁₂) in aerobic bacteria.