| Type: | Family | Name: | Cobaltochelatase subunit, putative |
| Description: | Cobaltochelatase is responsible for the insertion of cobalt into the corrin ring of coenzyme B12 during its biosynthesis. Cobalamin (vitamin B12) can be complexed with metal via ATP-dependent reactions (aerobic pathway) (e.g., in Pseudomonas denitrificans) or via ATP-independent reactions (anaerobic pathway) (e.g., in Salmonella typhimurium) [, ]. The corresponding cobalt chelatases are not homologous. The two versions have been well described. CbiK/CbiX is a monomeric, anaerobic version which acts early in the biosynthesis (). CobNST is a trimeric, ATP-dependent, aerobic version which acts late in the biosynthesis (//). The two pathways differ in the point of cobalt insertion during corrin ring formation []. There are apparently a number of variations on these two pathways, where the major differences seem to be concerned with the process of ring contraction [].A number of genomes (actinobacteria, cyanobacteria, betaproteobacteria and pseudomonads) which apparently biosynthesise B12, encode a cobN gene but are demonstrably lacking cobS and cobT. These genomes do, however contain a homologue, represented by this entry, of the magnesium chelatase subunits BchI/BchD family. Aside from the cyanobacteria (which have a separate magnesium chelatase trimer), these species do not make chlorins, so do not have any use for a magnesium chelatase. Furthermore, in nearly all cases the members of this family are proximal to either CobN itself or other genes involved in cobalt transport or B12 biosynthesis. Cobaltochelatase shows similarities with magnesium chelatase, which is also a complex ATP-dependent enzyme made up of two separable components. However, unlike the situation in cobaltochelatase, one of these two components is membrane bound in magnesium chelatase []. | Short Name: | Cob_chelat_sub_put |
