Magnesium-chelatase is a three-component enzyme that catalyses the insertion of Mg2+ into protoporphyrin IX. This is the first unique step in the synthesis of bacteriochlorophyll. 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:
protoporphyrin IX + Mg2+ + ATP + H
2O ADP + phosphate + Mg-protoporphyrin IX + 2 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 participates in porphyrin and chlorophyll metabolism.
Al-Karadaghi S; Hansson, A; Hansson, M; Olsen, JG; Gough, S; Willows, RD; Al-Karadaghi, S (2001). "Interplay between an AAA module and an integrin I domain may regulate the function of magnesium chelatase". J. Mol. Biol. 311 (1): 111–22. doi:10.1006/jmbi.2001.4834. PMID11469861.