The magnitude of changes in carboxylation capacity in dominant plant species under long-term elevated CO2 exposure (elevated pCa) directly impacts ecosystem CO2 assimilation from the atmosphere. We analyzed field CO2 response curves of 16 C3 species of different plant growth forms in favorable growth conditions in four free-air CO2 enrichment (FACE) experiments in a pine and deciduous forest, a...

(1) Activation of rat liver mitochondrial functions following glucagon treatment was demonstrated in mitochondria that had not been isolated by the conventional technique of differential centrifugation and washing in sucrose solutions. Crude liver homogenates in 0.3 M-sucrose or 0.15 M-KCI prepared from rats treated with glucagon showed stimulation of State-3 and uncoupled respiration, carboxyl...

Reaction 1, the carboxylation of acety-CoA to form malonylCo& is catalyzed by acetyl-CoA carboxylase, a biotin enzyme (l-6). Reaction 2, the reaction of acetyl-CoA with 7 moles of malonyl-CoA and 14 moles of TPNH to form palmitate, is an incompletely understood complex reaction catalyzed by palmitate synthetase (7-10). In recent years, there has been a number of observations (11-13) demonstrati...

Ribulose-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. Residues...

Stands of Scirpus olneyi, a native saltmarsh sedge with C3 photosynthesis, had been exposed to normal ambient and elevated atmospheric CO2 concentrations (Ca) in their native habitat since 1987. The objective of this investigation was to characterize the acclimation of photosynthesis of Scirpus olneyi stems, the photosynthesizing organs of this species, to long-term elevated Ca treatment in rel...

Woronick and Johnson (1) observed in Aspergillus niger extracts a pyruvate carboxylating system requiring adenosine triphosphate, but not involving phosphopyruvate, and suggested that the carboxylation reaction was coupled with the conversion of adenosine triphosphate to adenosine diphosphate and inorganic phosphate. Utter and Keech (2) studied a similar reaction in extracts of avian and beef l...

1. A simple kinetic method was devised to show whether dissolved CO2 orHCO3ion is the substrate in enzyme-catalysed carboxylation reactions. 2. The timecourse of the reductive carboxylation of 2-oxoglutarate by NADPH, catalysed by isocitrate dehydrogenase, was studied by a sensitive fluorimetric method at pH 7-3 and pH 6-4, with large concentrations of substrate and coenzyme and small carbon di...

The present work is concerned with an enzyme, obtained from an acetone powder of spinach leaves, which catalyzes the carboxylation of phosphorylenolpyruvate’ to yield, under the conditions of isolation here employed, oxalacetate and inorganic phosphate. Pyruvate or pyruvate plus ATP will not substitute for PEP. Reduced triphosphopyridine nucleotide is not added to the reaction mixture and malat...