Rubisco function, evolution, and engineering

TL;DR

This paper reviews the structure, evolution, and biochemical trade-offs of rubisco, the key enzyme in carbon fixation, and discusses efforts to engineer improved variants to enhance plant growth.

Contribution

It provides a comprehensive analysis of rubisco's evolutionary constraints and summarizes recent engineering approaches to improve its catalytic efficiency.

Findings

Rubisco's slow catalytic rate is due to inherent biochemical trade-offs.

Evolution has optimized rubisco for specific environments, limiting its overall efficiency.

Engineering efforts have shown potential to enhance rubisco performance in plants.

Abstract

Carbon fixation is the process by which CO2 is converted from a gas into biomass. The Calvin Benson Bassham (CBB) cycle is the dominant carbon fixation pathway on earth, driving >99.5% of the ~120 billion tons of carbon that are "fixed" as sugar, by plants, algae and cyanobacteria. The carboxylase enzyme in the CBB, ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco), fixes one CO2 molecule per turn of the cycle. Despite being critical to the assimilation of carbon, rubisco's kinetic rate is not very fast and it is a bottleneck in flux through the pathway. This presents a paradox - why hasn't rubisco evolved to be a better catalyst? Many hypothesize that the catalytic mechanism of rubisco is subject to one or more trade-offs, and that rubisco variants have been optimized for their native physiological environment. Here we review the evolution and biochemistry of rubisco through the lens of structure and mechanism in order to understand what trade-offs limit its improvement. We also review the many attempts to improve rubisco itself and, thereby, promote plant growth.