Technological and medical advances over the past few decades epitomize human capabilities. However, the increased life expectancies and concomitant land-use changes have significantly contributed to the release of ∼830 gigatons of CO into the atmosphere over the last three decades, an amount comparable to the prior two and a half centuries of CO emissions. The United Nations has adopted a pledge to achieve "net zero", i.
View Article and Find Full Text PDFThe enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) and its central role in capturing atmospheric CO via the Calvin-Benson-Bassham (CBB) cycle have been well-studied. Previously, a form II RuBisCO from , a facultative anaerobic bacterium, was shown to assemble into a hexameric holoenzyme. Unlike previous studies with form II RuBisCO, the enzyme could be crystallized in the presence of the transition state analogue 2-carboxyarabinitol 1,5-bisphosphate (CABP), greatly facilitating the structure-function studies reported here.
View Article and Find Full Text PDFRibulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) is a ubiquitous enzyme that catalyzes the conversion of atmospheric CO into organic carbon in primary producers. All naturally occurring RubisCOs have low catalytic turnover rates and are inhibited by oxygen. Evolutionary adaptations of the enzyme and its host organisms to changing atmospheric oxygen concentrations provide an impetus to artificially evolve RubisCO variants under unnatural selective conditions.
View Article and Find Full Text PDFRubisCO, the CO fixing enzyme of the Calvin-Benson-Bassham (CBB) cycle, is responsible for the majority of carbon fixation on Earth. RubisCO fixes CO faster than CO resulting in C-depleted biomass, enabling the use of δ C values to trace CBB activity in contemporary and ancient environments. Enzymatic fractionation is expressed as an ε value, and is routinely used in modelling, for example, the global carbon cycle and climate change, and for interpreting trophic interactions.
View Article and Find Full Text PDFBackground: With increasing concerns over global warming and depletion of fossil-fuel reserves, it is attractive to develop innovative strategies to assimilate CO, a greenhouse gas, into usable organic carbon. Cell-free systems can be designed to operate as catalytic platforms with enzymes that offer exceptional selectivity and efficiency, without the need to support ancillary reactions of metabolic pathways operating in intact cells. Such systems are yet to be exploited for applications involving CO utilization and subsequent conversion to valuable products, including biofuels.
View Article and Find Full Text PDFMetagenomic studies recently uncovered form II/III RubisCO genes, originally thought to only occur in archaea, from uncultivated bacteria of the candidate phyla radiation (CPR). There are no isolated CPR bacteria and these organisms are predicted to have limited metabolic capacities. Here we expand the known diversity of RubisCO from CPR lineages.
View Article and Find Full Text PDFUnlabelled: Recapturing atmospheric CO2 is key to reducing global warming and increasing biological carbon availability. Ralstonia eutropha is a biotechnologically useful aerobic bacterium that uses the Calvin-Benson-Bassham (CBB) cycle and the enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) for CO2 utilization, suggesting that it may be a useful host to bioselect RubisCO molecules with improved CO2 -capture capabilities. A host strain of R.
View Article and Find Full Text PDFRibulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) is a critical yet severely inefficient enzyme that catalyses the fixation of virtually all of the carbon found on Earth. Here, we report a functional metagenomic selection that recovers physiologically active RubisCO molecules directly from uncultivated and largely unknown members of natural microbial communities. Selection is based on CO2 -dependent growth in a host strain capable of expressing environmental deoxyribonucleic acid (DNA), precluding the need for pure cultures or screening of recombinant clones for enzymatic activity.
View Article and Find Full Text PDFThe first x-ray crystal structure has been solved for an activated transition-state analog-bound form II ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). This enzyme, from Rhodopseudomonas palustris, assembles as a unique hexamer with three pairs of catalytic large subunit homodimers around a central 3-fold symmetry axis. This oligomer arrangement is unique among all known Rubisco structures, including the form II homolog from Rhodospirillum rubrum.
View Article and Find Full Text PDFRibulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (Rubisco) is a globally significant biocatalyst that facilitates the removal and sequestration of CO2 from the biosphere. Rubisco-catalyzed CO2 reduction thus provides virtually all of the organic carbon utilized by living organisms. Despite catalyzing the rate-limiting step of photosynthetic and chemoautotrophic CO2 assimilation, Rubisco is markedly inefficient as the competition between O2 and CO2 for the same substrate limits the ability of aerobic organisms to obtain maximum amounts of organic carbon for CO2-dependent growth.
View Article and Find Full Text PDFBackground: Ribulose-1,5-bisphosphate is the rate-limiting enzyme in photosynthesis. The catalytic large subunit of the green-algal enzyme from Chlamydomonas reinhardtii is approxiamtely 90% identical to the flowering-plant sequences, although they confer diverse kinetic properties. To identify the regions that may account for species variation in kinetic properties, directed mutagenesis and chloroplast transformation were used to create four amino-acid substitutions in the carboxy terminus of the Chlamydomonas large subunit to mimic the sequence of higher-specificity plant enzymes.
View Article and Find Full Text PDFRibulose 1,5-bisphosphate (RuBP) carboxylase/oxygenase (RubisCO) catalyses the key reaction by which inorganic carbon may be assimilated into organic carbon. Phylogenetic analyses indicate that there are three classes of bona fide RubisCO proteins, forms I, II and III, which all catalyse the same reactions. In addition, there exists another form of RubisCO, form IV, which does not catalyse RuBP carboxylation or oxygenation.
View Article and Find Full Text PDFThere are four forms of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) found in nature. Forms I, II, and III catalyse the carboxylation and oxygenation of ribulose 1,5-bisphosphate, while form IV, also called the Rubisco-like protein (RLP), does not catalyse either of these reactions. There appear to be six different clades of RLP.
View Article and Find Full Text PDFProximal Cys(172) and Cys(192) in the large subunit of the photosynthetic enzyme Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase; EC 4.1.1.
View Article and Find Full Text PDFMicrobiol Mol Biol Rev
December 2007
About 30 years have now passed since it was discovered that microbes synthesize RubisCO molecules that differ from the typical plant paradigm. RubisCOs of forms I, II, and III catalyze CO(2) fixation reactions, albeit for potentially different physiological purposes, while the RubisCO-like protein (RLP) (form IV RubisCO) has evolved, thus far at least, to catalyze reactions that are important for sulfur metabolism. RubisCO is the major global CO(2) fixation catalyst, and RLP is a somewhat related protein, exemplified by the fact that some of the latter proteins, along with RubisCO, catalyze similar enolization reactions as a part of their respective catalytic mechanisms.
View Article and Find Full Text PDFThe loop between alpha-helix 6 and beta-strand 6 in the alpha/beta-barrel of ribulose-1,5-bisphosphate carboxylase/oxygenase plays a key role in discriminating between CO2 and O2. Genetic screening in Chlamydomonas reinhardtii previously identified a loop-6 V331A substitution that decreases carboxylation and CO2/O2 specificity. Revertant selection identified T342I and G344S substitutions that restore photosynthetic growth by increasing carboxylation and specificity of the V331A enzyme.
View Article and Find Full Text PDFRibulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzes the rate-limiting step of photosynthetic CO(2) fixation and, thus, limits agricultural productivity. However, Rubisco enzymes from different species have different catalytic constants. If the structural basis for such differences were known, a rationale could be developed for genetically engineering an improved enzyme.
View Article and Find Full Text PDFThe loop between alpha-helix 6 and beta-strand 6 in the alpha/beta-barrel active site of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.
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