Rubisco Function, Evolution, and Engineering

Abstract

Carbon fixation is the process by which CO2 is converted from a gas into biomass. The Calvin–Benson–Bassham cycle (CBB) is the dominant carbon-consuming pathway on Earth, driving >99.5% of the ∼120 billion tons of carbon that are converted to 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 into bioavailable sugars. Despite being critical to the assimilation of carbon, rubisco's kinetic rate is not very fast, limiting flux through the pathway. This bottleneck presents a paradox: Why has rubisco not 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. Expected final online publication date for the Annual Review of Biochemistry, Volume 92 is June 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

From Rags to Riches: Exploiting the Calvin‐Benson‐Bassham Cycle for Biomanufacturing

“…An excellent review about RuBisCO was recently published by Prywes et al . ; [29] some of the enzyme characteristics relevant for biotechnology are discussed in this section.…”

“…In Form I’, II, III and II/III RuBisCOs, mostly found in prokaryotes, the whole enzyme is made by one or more L 2 dimers (Figure 1). The more evolutionarily‐recent Form I RuBisCOs, present in both prokaryotes and eukaryotes, are composed of both large subunits (LSUs) and small subunits (SSUs), disposed in a L 8 S 8 configuration [29–31] . Based on the experimental evidence thus far, Form II RuBisCOs are also the isoforms of the enzyme that are easier to express heterologously [24] …”

“…Catalytic parameters of RuBisCO have been considered limiting, but recent evidence shows that, in reality, these kinetic features are rather average among the known enzymes [32] . Multiple efforts made to improve these parameters have been met with limited success [29,33] . Apart from performing the carboxylation reaction, RuBisCO can also mediate the oxygenation of 1 using atmospheric O 2 .…”

Systematic exploration of bacterial form I rubisco maximal carboxylation rates

“…Over 99% of global carbon fixation is catalyzed by rubisco (1), probably the most abundant enzyme in the biosphere (2). Rubisco is mainly divided into four distinct forms (I, II, II/III, and III) and can be found in all domains of life, from plants to algae through autotrophic bacteria and archaea (3). Within this diversity, form I is by far the most abundant of the four forms: it is used by all plants and cyanobacteria and is responsible for almost all CO 2 fixation in nature (4).…”

A redundant chloroplast protein is co-opted by potyvirids as the scaffold protein to mediate viral intercellular movement complex assembly

“…During photosynthetic pathway, ribulose 1, 5-bisphosphate carboxylase/oxygenase (Rubisco) is responsible for catalyzing the first rate-limiting step in CO 2 fixation. Rubisco is comprised of eight large subunits (RbCL; ∼50-55 kDa) and eight small subunits (RbCS; ∼12-18 kDa) which form a hexadecameric L 8 S 8 complex (Bracher et al, 2017; Mao et al, 2023; Prywes et al, 2023). RbCL is encoded by chloroplast genome, whereas RbCS is nucleus-encoded (Bracher et al, 2017).…”