Nonequilibrium Isotope Exchange Reveals a Catalytically Significant Enzyme-Phosphate Complex in the ATP Hydrolysis Pathway of the AAA~+ ATPase Magnesium Chelatase

摘要

Magnesium chelatase is an AAA+ ATPase that catalyzes the first committed step in chlorophyll biosynthesis. Using nonequilibrium isotope exchange, we show that the ATP hydrolysis reaction proceeds via an enzyme-phosphate complex. Exchange from radiolabeled phosphate to ATP was not observed, offering no support for an enzyme-ADP complex.