CARBON DIOXIDE FIXATION AND PHOSPHOENOLPYRUVATE CARBOXYLASE IN FERROBACILLUS FERROOXIDANS

1967 ◽  
Vol 13 (11) ◽  
pp. 1413-1419 ◽  
Author(s):  
George A. Din ◽  
Isamu Suzuki ◽  
Howard Lees
Keyword(s):  
Carbon Dioxide ◽  
Phosphoenolpyruvate Carboxylase ◽  
Metabolic Regulation ◽  
Carbon Dioxide Fixation ◽  
Acidic Ph ◽  
Ph Optimum ◽  
Carboxylase Activity ◽  
Intact Cells ◽  
Pep Carboxylase

Carbon dioxide fixation was studied in intact cells and cell-free extracts of Ferrobacillus ferrooxidans. The major pathways of fixation were found to be the carboxydismutase system and the phosphoenolpyruvate (PEP) carboxylase system. PEP carboxylase activity was shown to be under metabolic regulation, similar to the regulation established in heterotrophic microorganisms.Acetyl-CoA stimulated PEP carboxylase activity, while aspartate was inhibitory. The F. ferrooxidans enzyme appeared to have a neutral or acidic pH optimum, in contrast to the same enzyme isolated from heterotrophs.

Phosphoenolpyruvate carboxylase activity from Avena coleoptile tissue. Regulation by H+ and malate

1978 ◽  
Vol 56 (4) ◽  
pp. 404-407 ◽  
Author(s):  
B. C. Hill ◽  
A. W. Bown
Keyword(s):  
Phosphoenolpyruvate Carboxylase ◽  
Enzyme System ◽  
Mass Action ◽  
Direct Inhibition ◽  
Carboxylase Activity ◽  
Pep Carboxylase ◽  
Action Effect ◽  
Avena Coleoptile ◽  
Oxaloacetic Acid ◽  
Regulatory Properties

Preparations of phosphoenolpyruvate (PEP) carboxylase activity from Avenu sativa coleoptile tissue were assayed by measuring the incorporation of labelled bicarbonate into a derivative of oxaloacetic acid or by coupling oxaloacetic acid production to malate dehydrogenase activity and the oxidation of NADH. Malate inhibition of PEP carboxylase activity was found to be noncompetitive, was not due to a mass action effect on the coupled enzyme system or to chelation of Mg2+, and probably involved direct inhibition of the enzyme by malate. Maximal PEP carboxylase activity was exhibited around pH 8.0 and increased 125% between pH 7.0 and pH 7.6. Inhibition by 4 mML-malate was virtually complete at pH 7.0 and decreased to 10% inhibition at pH 8. This information is discussed in the light of data which demonstrates that in response to IAA. coleoptile tissue accumulates malate and secretes H+. The regulatory properties of PEP carboxylase are consistent with a role in malate production which could resist increases in intracellular pH resulting from an auxin-stimulated H+ efflux.

Carbon dioxide fixation by cell-free extracts of group D streptococci

1969 ◽  
Vol 15 (1) ◽  
pp. 61-66 ◽  
Author(s):  
Victor F. Lachica ◽  
Paul A. Hartman
Keyword(s):  
Carbon Dioxide ◽  
Pyruvate Carboxylase ◽  
Carbon Dioxide Fixation ◽  
Pep Carboxylase ◽  
Streptococcus Faecium ◽  
Pep Carboxykinase ◽  
Group D

Cell-free extracts of group D streptococci incorporated 14CO2 into aspartate. Pyruvate was the acceptor of CO2 for Streptococcus faecium; phosphoenolpyruvate was the CO2 acceptor for S. bovis; and both substrates were CO2 acceptors for S. faecalis. The enzymes, by which the CO2 fixation was effected, appear to be pyruvate carboxylase for S. faecium, phosphoenolpyruvate (PEP) carboxykinase and PEP carboxylase for S. bovis, and pyruvate carboxylase and PEP carboxykinase for S. faecalis.

Inhibition of phosphoenolpyruvate carboxylase from C4 plants by malate and aspartate

1975 ◽  
Vol 53 (17) ◽  
pp. 1925-1933 ◽  
Author(s):  
S. C. Huber ◽  
G. E. Edwards
Keyword(s):  
Phosphoenolpyruvate Carboxylase ◽  
Maximum Velocity ◽  
C4 Plants ◽  
Digitaria Sanguinalis ◽  
Leaf Extracts ◽  
Ph Optimum ◽  
Pep Carboxylase ◽  
Assay Mixture ◽  
Acid Inhibitor ◽  
Rate Limiting

The activity of phosphoenolpyruvate carboxylase in leaf extracts of C4 plants has been shown to be inhibited by the C4 acids malate and aspartate. The magnitude of inhibition observed with phosphoenolpyruvate carboxylase from Digitaria sanguinalis leaves was dependent on the pH of the assay mixture and the concentration of phosphoenolpyruvate (PEP), Mg2+. and the C4 acid inhibitor. The percentage inhibition decreased with increasing pH up to 8.5. At rate-limiting concentrations of phosphoenolpyruvate the pH optimum of the enzyme was 7.8, whereas the enzyme partially inhibited by malate or aspartate had a pH optimum of roughly 8.3. Malate and aspartate inhibited the enzyme by increasing the apparent Km for phosphoenolpyruvate without altering the maximum velocity, such that inhibition was greatest at rate-limiting concentrations of PEP but was not observed at saturating (3 mM) substrate levels. Glucose-6-P. an activator of PEP carboxylase, decreased the apparent Km for PEP and reversed the inhibition by malate and aspartate. Inhibition was also dependent on the concentration of Mg2+. At 1 mM Mg2+, 1 mM malate caused 60% inhibition, but at 5 mM Mg2+ the inhibition was reduced to 15%. Mg2+ at concentrations from 1 to 5 mM had no effect on the apparent Km for PEP. With Sephadex extracts of PEP carboxylase from leaves of D. sanguinalis, malate and aspartate were equally inhibitory, with roughly 2 mM levels required for 50% inhibition. Both malate and aspartate were inhibitory with PEP carboxylase extracted from leaves of a variety of C4∙ but not C3∙ plants. The significance of the observed inhibition and activation of PEP carboxylase by metabolites is discussed in relation to C4 photosynthesis.

scholarly journals AN EXPERIMENTAL SEPARATION OF OXYGEN LIBERATION FROM CARBON DIOXIDE FIXATION IN PHOTOSYNTHESIS BY CHLORELLA

1943 ◽  
Vol 27 (1) ◽  
pp. 15-28 ◽  
Author(s):  
C. S. Fan ◽  
J. F. Stauffer ◽  
W. W. Umbreit
Keyword(s):  
Carbon Dioxide ◽  
Chlorella Pyrenoidosa ◽  
Carbon Dioxide Fixation ◽  
Intact Cells

Using intact cells of Chlorella pyrenoidosa it is possible to obtain oxygen by the reduction of certain reducible materials other than carbon dioxide. Of these, benzaldehyde was studied in some detail. This reduction does not involve the production of carbon dioxide from the benzaldehyde. Stoichiometrical relationships as expressed by the following equation: 2C6H5CHO + 2H2O → 2C6H5CH2OH + O2 are somewhat difficult to obtain because the benzaldehyde can disappear from the reaction mixtures by dark reactions. The technique is now available which permits detailed studies of the oxygen-liberating mechanisms in photosynthesis.

Phosphopyruvate carboxylase activity and carbon dioxide fixation via C4 acids over the division cycle in synchronized Euglena cultures

Planta ◽  
1971 ◽  
Vol 100 (2) ◽  
pp. 124-130 ◽  
Author(s):  
G. A. Codd ◽  
M. J. Merrett
Keyword(s):  
Carbon Dioxide ◽  
Carbon Dioxide Fixation ◽  
Carboxylase Activity

The Uptake of Adenine by Isolated Human Platelet Membranes

1974 ◽  
Vol 32 (02/03) ◽  
pp. 457-464
Author(s):  
Paul C. French ◽  
Jan J. Sixma ◽  
Holm Holmsen
Keyword(s):  
Human Platelet ◽  
Facilitated Diffusion ◽  
Adenine Phosphoribosyltransferase ◽  
Ph Optimum ◽  
Intact Cells ◽  
Platelet Membranes ◽  
Group Translocation ◽  
Triton X

SummaryAdenine uptake into isolated platelet membranes had about the same Km (151 ± 21 • 9 nM) as uptake into intact cells (159 ± 21 nM) and was also competitively inhibited by papaverine and hypoxanthine. No uptake occurred at 0° and accumulated adenine was converted to AMP. AMP was not firmly bound to protein as judged by chromatography of triton X-100 solubilized membranes on Sephadex G25. The pH optimum for adenine uptake was at pH 5-5. Exogenous 5-phosphoribosyl-l-pyrophos- phate strongly stimulated uptake. These data may be explained by uptake of adenine by facilitated diffusion followed by conversion to AMP by adenine phosphoribosyltransferase but group translocation cannot be entirely excluded.

V. CARBON DIOXIDE FIXATION AND SUBSTRATE OXIDATION IN THE CHEMOSYNTHETIC SULFUR AND HYDROGEN BACTERIA

1962 ◽  
Vol 26 (2_Pt_1-2) ◽  
pp. 168-175 ◽  
Author(s):  
Wolf Vishniac ◽  
Philip A. Trudinger
Keyword(s):  
Carbon Dioxide ◽  
Substrate Oxidation ◽  
Carbon Dioxide Fixation ◽  
Hydrogen Bacteria

scholarly journals Chester H. Werkman and Merton F. Utter: Using Bacteria Juice and 13C to Explore Carbon Dioxide Fixation

2005 ◽  
Vol 280 (16) ◽  
pp. e13-e14
Author(s):  
Nicole Kresge ◽  
Robert D. Simoni ◽  
Robert L. Hill
Keyword(s):  
Carbon Dioxide ◽  
Carbon Dioxide Fixation
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