magnesium chelatase

{{Short description|Enzyme}}

{{infobox enzyme

| Name = Magnesium chelatase

| EC_number = 6.6.1.1

| CAS_number = 9074-88-8

| GO_code = 0016851

| image = 2x31.jpg

| width = 270

| caption = Magnesium chelatase hetero12mer, Rhodobacter capsulatus

}}

{{Pfam box |Symbol = Mg_chelatse_chII |Name = Magnesium chelatase, ChlI subunit |Pfam = PF01078 |InterPro = IPR000523 |PROSITE = |PDB = {{PDB|1g8p}} }}

{{Pfam box |Symbol = CobN/Mg_chltase |Name = CobN/magnesium chelatase |Pfam = PF02514 |InterPro = IPR003672 |PROSITE = |PDB = }}

Magnesium-chelatase is a three-component enzyme ({{EnzExplorer|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.{{cite journal |title=Biosynthesis of chlorophylls from protoporphyrin IX |last =Willows | first =Robert D. | journal =Natural Product Reports | year =2003 | volume = 20 |issue = 6 | pages =327–341 |doi=10.1039/B110549N |pmid=12828371}}{{cite journal |doi=10.1007/s11120-006-9076-6 |title=Recent advances in chlorophyll biosynthesis |year=2007 |last1=Bollivar |first1=David W. |journal=Photosynthesis Research |volume=90 |issue=2 |pages=173–194 |pmid=17370354 |s2cid=23808539 }} 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:

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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.