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 (bacterio)chlorophyll. Due to this, it is thought that Mg-chelatase has an important ro ...
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 (bacterio)chlorophyll. Due to this, it is thought that Mg-chelatase has an important role in channelling inter- mediates into the (bacterio)chlorophyll branch in response to conditions suitable for photosynthetic growth. ChlI and BchD have molecular weight between 38-42 kDa.
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.