CATH Classification

Domain Context

CATH Clusters

Superfamily 3.40.50.1400
Functional Family Sirohydrochlorin cobaltochelatase CbiKP

Enzyme Information

4.99.1.4
Sirohydrochlorin ferrochelatase.
based on mapping to UniProt Q72EC8
Siroheme + 2 H(+) = sirohydrochlorin + Fe(2+).
-!- This enzyme catalyzes the third of three steps leading to the formation of siroheme from uroporphyrinogen III. -!- The first step involves the donation of two S-adenosyl-L-methionine- derived methyl groups to carbons 2 and 7 of uroporphyrinogen III to form precorrin-2 (EC 2.1.1.107) and the second step involves an NAD(+)-dependent dehydrogenation to form sirohydrochlorin from precorrin-2 (EC 1.3.1.76). -!- In Saccharomyces cerevisiae, the last two steps are carried out by a single bifunctional enzyme, Met8p. -!- In some bacteria, steps 1-3 are catalyzed by a single multifunctional protein called CysG, whereas in Bacillus megaterium, three separate enzymes carry out each of the steps, with SirB being responsible for the above reaction.
4.99.1.3
Sirohydrochlorin cobaltochelatase.
based on mapping to UniProt Q72EC8
Cobalt-sirohydrochlorin + 2 H(+) = sirohydrochlorin + Co(2+).
-!- 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.

UniProtKB Entries (1)

Q72EC8
CBIKP_DESVH
Desulfovibrio vulgaris str. Hildenborough
Sirohydrochlorin cobaltochelatase CbiKP

PDB Structure

PDB 2XVZ
External Links
Method X-RAY DIFFRACTION
Organism
Primary Citation
Evolution in a Family of Chelatases Facilitated by the Introduction of Active Site Asymmetry and Protein Oligomerization.
Romao, C.V., Ladakis, D., Lobo, S.A.L., Carrondo, M.A., Brindley, A.A., Deery, E., Matias, P.M., Pickersgill, R.W., Saraiva, L.M., Warren, M.J.
Proc.Natl.Acad.Sci.USA