| Type: | Family | Name: | Co/Fe-chelatase, CbiX-related |
| Description: | This group represents proteins that contain an N-terminal CbiX (class II chelatase) domain, and an additional unique C-terminal domain of unknown function.This group of proteins is able to chelate both Fe2+and Co2+and can therefore act in both sirohaem and cobalamin biosynthesis []. It functions primarily as a cobaltochelatase that inserts cobalt into sirohydrochlorin during the biosynthesis of cobalamin (vitamin B12) [, ]. This form of the enzyme contains two copies of the cobalamin biosynthesis CbiX domain (),while the stand-alone form contains one (). A similar protein named SirB (YlnE, also a member of ), encoded within a small sirohaem biosynthetic operon, has been shown to be capable of inserting ferrous iron into sirohydrochlorin during the biosynthesis of sirohaem [].Members of this family belong to the class II chelatases, which are defined as homomeric monofunctional chelatases that do not require ATP for catalysis []. Class II chelatases include, in addition to CbiX and SirB, cobaltochelatase CbiK () and protoporphyrin ferrochelatase HemH () []. All of these enzymes share some distant sequence similarity, and CbiK and HemH have a similar overall topology [], which is also predicted for CbiX. It has been suggested that class II chelatases may have evolved from a primordial CbiXStype of enzyme []. | Short Name: | CbiX-rel |
