Crystal structures of cyanobacterial light-dependent protochlorophyllide oxidoreductase

Significance Photoenzymes use light as an energy source to catalyze chemical reactions and can be engineered as environmental-friendly biocatalysts. The LPOR, an enzyme late in the biosynthesis of chlorophyll, is one of the few naturally occurring photoenzymes. However, limited structural information prevents understanding of its working mechanism. In this study, we report two structures of cyanobacterial LPOR bound to NADPH, which reveals the molecular basis of a NADPH-binding pocket, a substrate cavity, and the proton-relay path. Our findings will help to elucidate and design the light-driven enzymes for the future development of photocatalysis.