Magnesium chelatase

Magnesium-chelatase is a three-component enzyme (EC 6.6.1.1) that catalyses the insertion of Mg²⁺ into protoporphyrin IX. This is the first unique step in the synthesis of chlorophyll and bacteriochlorophyll.^[1][2] As a result, it is thought that Mg-chelatase has an important role in channeling intermediates into the (bacterio)chlorophyll branch in response to conditions suitable for photosynthetic growth:

Magnesium chelatase
Magnesium chelatase hetero12mer, Rhodobacter capsulatus
Identifiers
EC no.	6.6.1.1
CAS no.	9074-88-8
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

Magnesium chelatase, ChlI subunit
Identifiers
Symbol	Mg_chelatse_chII
Pfam	PF01078
InterPro	IPR000523
Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary PDB PDB: 1g8p​

CobN/magnesium chelatase
Identifiers
Symbol	CobN/Mg_chltase
Pfam	PF02514
InterPro	IPR003672
Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

protoporphyrin IX + Mg²⁺
+ ATP + H
₂O ${\displaystyle \rightleftharpoons }$ ADP + phosphate + Mg-protoporphyrin IX + 2 H⁺

The four substrates of this enzyme are ATP, protoporphyrin IX, Mg²⁺, and H₂O; its four products are ADP, phosphate, Mg-protoporphyrin IX, and H⁺.

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 Mg-protoporphyrin IX magnesium-lyase. Other names in common use include protoporphyrin IX magnesium-chelatase, protoporphyrin IX Mg-chelatase, magnesium-protoporphyrin IX chelatase, magnesium-protoporphyrin chelatase, magnesium-chelatase, Mg-chelatase, and Mg-protoporphyrin IX magnesio-lyase. This enzyme is part of the biosynthetic pathway to chlorophylls.

See also

• Biosynthesis of chlorophylls