Protochlorophyllide oxidoreductase: 'dark' reactionsof light-driven enzyme

The catalytic mechanism of NADPH:protochlorophyllide oxidoreductase involves two steps that do not require light and convert light-driven reaction products into photoactive intermediate and Chlide. Data indicate that the dark reactions occur at or above the 'glass transition' temperature of proteins, indicating that domain movement and/or structural reorganization of the protein is required for catalysis.