The activation of Rubisco in vivo requires the presence of the regulatory protein Rubisco activase. This enzyme facilitates the release of sugar phosphate inhibitors from Rubisco catalytic sites thereby influencing carbamylation. T(1) progeny of transgenic Flaveria bidentis (a C(4) dicot) containing genetically reduced levels of Rubisco activase were used to explore the role of the enzyme in C(...

Widely heralded as the most important enzyme on Earth, ribulose 1,5-bis-phosphate carboxylase/oxygenase (Rubisco) catalyzes the reaction that draws inorganic carbon into the biosphere during the Calvin-Benson cycle. In higher plants, algae, andcyanobacteria,Rubiscooccursasahexadecamer consisting of eight large (50 kD) subunits and eight small (13 to 15 kD) subunits. Whereas the large subunits a...

Ribulose-1,5-bisphosphate carboxylase (Rubisco) efficiency for CO2-saturated photosynthesis was examined in leaves of rice (Oryza sativa L.). The amount of Rubisco in a leaf was calculated to be 30-55% in excess for the light-saturated rate of photosynthesis at 100 Pa CO2. Long-term exposure to CO2 enrichment decreased the amount of Rubisco protein. However, N was not reallocated from decreased...

There 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. Although related to bona fide Rubisco proteins at th...

In photosynthesis Rubisco catalyses the assimilation of CO(2) by the carboxylation of ribulose-1,5-bisphosphate. However, the catalytic properties of Rubisco are not optimal for current or projected environments and limit the efficiency of photosynthesis. Rubisco activity is highly regulated in response to short-term fluctuations in the environment, although such regulation may not be optimally...

NITRIC OXIDE-ASSOCIATED1 (NOA1) encodes a circularly permuted GTPase (cGTPase) known to be essential for ribosome assembly in plants. While the reduced chlorophyll and Rubisco phenotypes were formerly noticed in both NOA1-suppressed rice and Arabidopsis, a detailed insight is still necessary. In this study, by using RNAi transgenic rice, we further demonstrate that NOA1 functions in a temperatu...

Net photosynthesis (Pn) is inhibited by moderate heat stress. To elucidate the mechanism of inhibition, we examined the effects of temperature on gas exchange and ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) activation in cotton and tobacco leaves and compared the responses to those of the isolated enzymes. Depending on the CO(2) concentration, Pn decreased when temperatures exceed...

Rubisco limits photosynthetic CO(2) fixation because of its low catalytic turnover rate (k(cat)) and competing oxygenase reaction. Previous attempts to improve the catalytic efficiency of Rubisco by genetic engineering have gained little progress. Here we demonstrate that the introduction of the small subunit (RbcS) of high k(cat) Rubisco from the C(4) plant sorghum (Sorghum bicolor) significan...

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), the key enzyme of the Calvin-Benson-Bassham cycle of photosynthesis, requires conformational repair by Rubisco activase for efficient function. Rubisco mediates the fixation of atmospheric CO2 by catalyzing the carboxylation of the five-carbon sugar ribulose-1,5-bisphosphate (RuBP). It is a remarkably inefficient enzyme, and efforts to ...