Chelatase activity of magnesium dechelatase associated with chlorophyll degradation.

Abstract

Metalated tetrapyrrole molecules play crucial roles in respiration, photosynthesis, and biocatalysis. In this study, the chelatase activity of the bacterial magnesium dechelatase homologous gene, which encodes an enzyme that extracts the central magnesium ion from chlorophyll, was demonstrated. The recombinant protein inserted metal ions, such as zinc, into methyl pyropheophorbide a, a synthetic derivative of chlorophyll a. Mutation analysis and structural modeling suggested H32, D34, and D62 as key residues involved in coordinating metal ions and facilitating proton extraction from methyl pyropheophorbide a. Chelatase activity was also found in the recombinant plant magnesium dechelatase protein. The bacterial gene complemented Escherichia coli ferrochelatase mutants. These findings provide novel insights into the mechanisms underlying chelation reactions.