Magnesium chelatase

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:

ATP + protoporphyrin IX + Mg₂+ + H₂O ADP + phosphate + Mg-protoporphyrin IX + 2 H⁺

The 4 substrates of this enzyme are ATP, protoporphyrin IX, Mg²⁺, and H₂O, whereas its 4 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 participates in porphyrin and chlorophyll metabolism.

References

• Walker CJ, Weinstein JD (1991). "In vitro assay of the chlorophyll biosynthetic enzyme Mg-chelatase: resolution of the activity into soluble and membrane-bound fractions". Proc. Natl. Acad. Sci. U. S. A. 88 (13): 5789–93. doi:10.1073/pnas.88.13.5789. PMC 51963. PMID 11607197. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=51963. 
• Walker CJ, Willows RD (Pt 2). "Mechanism and regulation of Mg-chelatase". Biochem. J. 327: 321–33. PMC 1218797. PMID 9359397. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1218797. 
• 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. PMID 11469861.