A deep dive into seagrass Rubisco catalytic properties uncovers a distinct evolutionary trajectory

Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the most abundant and arguably most important enzyme on Earth, as it is the entry point of carbon into the biosphere. CO2 fixation by Rubisco onto ribulose-1,5 bisphosphate (RuBP) is the first step in the Calvin–Benson–Bassham cycle, resulting in two molecules of 3-phosphoglycerate (3PGA), which ultimately make up the biomass of photosynthetic organisms. Efficient CO2 fixation is hindered by the inability of Rubisco to discriminate between CO2 and O2. Oxygenation of RuBP leads to the production of toxic 2-phosphoglycolate, which is recycled back to 3PGA via photorespiration, consuming energy and releasing CO2 in the process (Sage et al., 2012). In agriculturally important plants such as wheat (Triticum aestivum) or rice (Oryza sativa), photorespiration can cause losses greater than 25% of the CO2 assimilated by photosynthesis (Walker et al., 2016), making Rubisco a key target for improving crop photosynthesis.