Rubisco, the imperfect winner: "it's all about the base".

Since the discovery of Rubisco as the Fraction 1 protein initially named by Sam Wildman, Rubisco has attracted significant efforts to examine the nature of catalysis and whether diversity exists among photosynthetic organisms. Early studies demonstrate the influence of Rubisco on carbon assimilation and its control over the flux of carbon through the Calvin-Benson-Bassham cycle, which is closely linked to the catalytic properties of the enzyme. Understanding Rubisco catalysis is complex and includes an activation step through the formation of a carbamate at the conserved active site lysine residue and the formation of a highly reactive enediol that is the key to its catalytic reaction. The formation of this enediol is both the basis of its success and its Achilles heel, creating imperfections to its catalytic efficiency. While Rubisco originally evolved in an atmosphere of high CO2, the earth's multiple oxidation events provided challenges to Rubisco through the fixation of O2 that competes with CO2 at the active site. Numerous catalytic screens across the Rubisco superfamily has identified significant variation in catalytic properties that have been linked to large and small subunit sequences. Despite this, we still have a rudimentary understanding of Rubiscos' catalytic mechanism and how the evolution of kinetic properties has occurred. This review identifies the lysine base which functions both as an activator and a proton abstractor to create the enediol, as a key to understanding how Rubisco may change its kinetic properties. This review discusses the ways in which Rubisco and its partners have overcome catalytic imperfections and thrived in a world of high O2, low CO2 and variable climatic regimes.