ATPases and phosphate exchange activities in magnesium chelatase subunits of Rhodobacter sphaeroides

Research output: Contribution to journalArticle


Three separate proteins, BchD, BchH, and BchI, together with ATP, insert magnesium into protoporphyrin IX. An analysis of ATP utilization by the subunits revealed the following: BchH catalyzed ATP hydrolysis at the rate of 0.9 nmol per min per mg of protein. BchI and BchD, tested individually, had no ATPase activity but, when combined, hydrolyzed ATP at the rate of 117.9 nmol/min per mg of protein. Magnesium ions were required for the ATPase activities of both BchH and BchI+D, and these activities were inhibited 50% by 2 mM o-phenanthroline. BchI additionally catalyzed a phosphate exchange reaction from ATP and ADP. We conclude that ATP hydrolysis by BchI+D is required for an activation step in the magnesium chelatase reaction, whereas ATPase activity of BchH and the phosphate exchange activity of BchI participate in subsequent reactions leading to the insertion of Mg2+ into protoporphyrin IX.


External organisations
  • Carlsberg Research Center / Carlsberg Laboratory
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Biochemistry and Molecular Biology


  • Adenosine Diphosphate/metabolism, Adenosine Triphosphatases/antagonists & inhibitors/*metabolism, Enzyme Activation, Enzyme Inhibitors/pharmacology, Lyases/antagonists & inhibitors/chemistry/*metabolism, Phenanthrolines/pharmacology, Phosphates/*metabolism, Protoporphyrins/chemistry, Rhodobacter sphaeroides/*enzymology, Sodium Fluoride/pharmacology
Original languageEnglish
Pages (from-to)13351-13356
JournalProceedings of the National Academy of Sciences
Issue number24
Publication statusPublished - 1997
Publication categoryResearch
Externally publishedYes

Bibliographic note