Cofactors

There are no Cofactors for this Enzyme

Reaction Mechanism

magnesium chelatase By Reference

Magnesium chelatase has a vital role in chlorophyll biosynthesis, using the energy from ATP hydrolysis to insert a Mg(II) ion into a porphyrin ring. It is part of a generic family of cellular ATPases known as AAA, displaying homology in particular to Cobalt Chelatase. Three subunits make up the overall protein in bacteria, BchI, BChlH and BChlD, also conserved in higher organisms. BChlI has ATPase activity and BChlH binds to the protoporphyrin group while BChlD has an regulatory allosteric role. Currently, there is limited experimental evidence to confirm a formal mechanism of magnesium chelatase with Arg 289 in BChlI being the only identifiable catalytic residue.




Binding of the porphyrin.BChlH complex and the Magnesium triggers the release of the ATP binding site of the BChI subunit which is able to hydrolyse ATP. The hydrolysis of ATP proceeds via the nucleophilic attack of a water molecule on the gamma phosphate, to form a pentavalent transition state stabilised by Arg 289. This collapses to release the products ADP and Pi, causing subunit motion which results in the transfer of Mg2+ to the porphyrin.

Catalytic Residues

AA	Uniprot	Uniprot Resid	PDB	PDB Resid
Arg	P26239	289	1g8p	289
View Reaction Mechanisms in M-CSA

Reaction Parameters

• Kinetic Parameters

  Organism	KM Value [mM]	Substrate	Comment
  Thermosynechococcus vestitus	0.0028	Mg2+	pH 7.7, 45°C

• Temperature

  There are no reaction parameters information for this Enzyme.

• pH

  There are no reaction parameters information for this Enzyme.

Associated Proteins

Citations

• Conformational variability of cyanobacterial ChlI, the AAA+ motor of magnesium chelatase involved in chlorophyll biosynthesis.
• A point mutation in the gene encoding magnesium chelatase I subunit influences strawberry leaf color and metabolism.
• Conformational variability of cyanobacterial ChlI, the AAA+ motor of magnesium chelatase involved in chlorophyll biosynthesis
• Magnesium chelatase subunit D is not only required for chlorophyll biosynthesis and photosynthesis, but also affecting starch accumulation in Manihot esculenta Crantz.
• Magnesium chelatase subunit D is not only required for chlorophyll biosynthesis and photosynthesis, but also affecting starch accumulation in Manihot esculenta Crantz
• A mutation in SlCHLH encoding a magnesium chelatase H subunit is involved in the formation of yellow stigma in tomato (Solanum lycopersicum L.).
• A mutation in SlCHLH encoding a magnesium chelatase H subunit is involved in the formation of yellow stigma in tomato (Solanum lycopersicum L.)
• The active site of magnesium chelatase.
• Photorespiration Regulates Carbon-Nitrogen Metabolism by Magnesium Chelatase D Subunit in Rice.
• Multiallelic, Targeted Mutagenesis of Magnesium Chelatase With CRISPR/Cas9 Provides a Rapidly Scorable Phenotype in Highly Polyploid Sugarcane.
• Heterologous Expression of the Barley (Hordeum vulgare L.) Xantha-f, -g and -h Genes that Encode Magnesium Chelatase Subunits.