scholarly journals Pyrophosphate:fructose 6-phosphate 1-phosphotransferase and glycolysis in non-photosynthetic tissues of higher plants

1985 ◽  
Vol 227 (1) ◽  
pp. 299-304 ◽  
Author(s):  
T ap Rees ◽  
J H Green ◽  
P M Wilson
Keyword(s):  
Pisum Sativum ◽  
Beta Vulgaris ◽  
Higher Plants ◽  
Starch Synthesis ◽  
Carbohydrate Oxidation ◽  
Allium Porrum ◽  
Catalytic Activities ◽  
Net Flux ◽  
Arum Maculatum ◽  
Fructose 1,6 Bisphosphate

The activity of pyrophosphate:fructose-6-phosphate 1-phosphotransferase [PFK (PPi); EC 2.7.1.90] in extracts of the storage tissues of leek (Allium porrum), beetroot (Beta vulgaris) and roots of darnel (Lolium temulentum) exceeded 0.15 mumol/min per g fresh wt. As net flux from fructose 1,6-bisphosphate to fructose 6-phosphate in these tissues is unlikely, it is suggested that PFK (PPi) does not contribute to gluconeogenesis or starch synthesis. The maximum catalytic activities of PFK (PPi) in apex, stele and cortex of the root of pea (Pisum sativum) and in the developing and the thermogenic club of the spadix of cuckoo-pint (Arum maculatum) were measured and compared with those of phosphofructokinase, and to estimates of the rates of carbohydrate oxidation. PPi and fructose 2,6-bisphosphate in Arum clubs were measured. The above measurements are consistent with a glycolytic role for PFK (PPi) in tissues where there is marked biosynthesis, but not in the thermogenic club of Arum. The possibility that PFK (PPi) is a means of synthesizing pyrophosphate is discussed.

scholarly journals Lack of fructose-1,6-bisphosphatase in a range of higher plants that store starch

1990 ◽  
Vol 271 (2) ◽  
pp. 467-472 ◽  
Author(s):  
G Entwistle ◽  
T ap Rees
Keyword(s):  
Potato Tuber ◽  
Sweet Corn ◽  
Higher Plants ◽  
Starch Synthesis ◽  
Significant Activity ◽  
Higher Plant ◽  
White Horse ◽  
Fructose 1,6 Bisphosphatase ◽  
Pea Roots ◽  
Fructose 1,6 Bisphosphate

The aim of this work was to discover whether fructose-1,6-bisphosphatase (FBPase) is present in higher-plant cells that synthesize storage starch. The following were examined: suspension cultures of soybean (Glycine max), tubers of potato (Solanum tuberosum), florets of cauliflower (Brassica oleracea), developing endosperm of maize and of sweet corn (Zea mays), roots of pea (Pisum sativum), and the developing embryos of round and wrinkled varieties of pea. Unfractionated extracts of each tissue readily converted fructose 1,6-bisphosphate to fructose 6-phosphate in assays for both plastidic and cytosolic FBPase. These conversions were not inhibited by 20 microM-fructose 2,6-bisphosphate. Except in extracts of pea embryos and sweet-corn endosperm, treatment with affinity-purified antibodies to pyrophosphate: fructose-6-phosphate 1-phosphotransferase reduced the above fructose 6-phosphate production to the rate found with boiled extracts. The antibody-resistant activity from sweet corn was slight. In immunoblot analyses, antibody to plastidic FBPase did not react positively with any protein in extracts of soybean cells, potato tuber, cauliflower florets, maize endosperm and pea roots. Positive reactions were found for extracts of embryos of both round and wrinkled varieties of peas and endosperm of sweet corn. For pea embryos, but not for sweet-corn endosperm, the Mr of the recognized protein corresponded to that of plastidic FBPase. It is argued that soybean cells, potato tuber, cauliflower florets, maize (var. White Horse Tooth) endosperm and pea roots lack significant activity of plastidic FBPase, but that this enzyme is present in developing embryos of pea. The data for sweet corn (var. Golden Bantam) are not decisive. It is also argued that, where FBPase is absent, carbon for starch synthesis does not enter the amyloplast as triose phosphate.

Nucleotide sugars and starch synthesis in spadix of Arum maculatum and suspension cultures of Glycine max

1984 ◽  
Vol 23 (11) ◽  
pp. 2463-2468 ◽  
Author(s):  
T. ap Rees ◽  
M. Leja ◽  
F.D. Macdonald ◽  
J.H. Green
Keyword(s):  
Glycine Max ◽  
Starch Synthesis ◽  
Suspension Cultures ◽  
Nucleotide Sugars ◽  
Arum Maculatum

Properties and Subcellular Localization of ʟ-Alanine: Aldehyde Aminotransferase: Concept of an Ubiquitous Plant Enzyme Involved in Secondary Metabolism

1981 ◽  
Vol 36 (7-8) ◽  
pp. 625-632 ◽  
Author(s):  
Coralie Wink ◽  
Thomas Hartmann
Keyword(s):  
Subcellular Localization ◽  
Secondary Metabolism ◽  
Spinacia Oleracea ◽  
Higher Plants ◽  
Ph Dependence ◽  
Metabolic Function ◽  
Aliphatic Aldehydes ◽  
Low Levels ◽  
Arum Maculatum ◽  
Plant Enzyme

Abstract L-Alanine: aldehyde aminotransferase occurs ubiquitously in higher plants. The enzyme catalyzes the reaction: L-alanine + monoaldehyde -> monoamine + pyruvate; it is responsible for the formation of aliphatic plant amines and involved in the biosynthesis of hemlock alkaloids as shown by Roberts. A continuous coupled photometric test was developed to determine the low activities of the transaminase. The enzyme from the "amine-free" plant Spinacia oleracea was purified 77-fold and separated from other aminotransferases. A comparison of the Spinacia enzyme with that isolated from spadix-appendices of the amine-producing Arum maculatum during anthesis revealed very similar characteristics in pH-dependence, ATm-values for alanine and aliphatic aldehydes, and inhibition by 2-oxoacids. In contrast to the Spinacia enzyme the Arum aminotransferase is rapidly inactivated in the absence of pyridoxal-5'-phosphate. The enzymes of S. oleracea, A. maculatum and Mercurialis perennis are localized in mitochondria, but not in chloroplasts or peroxisomes. The results are discussed in relation to the function of alanine: aldehyde aminotransferase in secondary metabolism. It is suggested that some enzymes may be expressed in plants at low levels, even in the absence of any metabolic function.

Starch Synthesis and Carbohydrate Oxidation In Developing Potato Tuber Amyloplasts

2000 ◽  
Vol 3 (5) ◽  
pp. 892-895
Author(s):  
Muhammad Naeem . ◽  
Michael J. Emes . ◽  
M. Yasin Ashraf .
Keyword(s):  
Potato Tuber ◽  
Starch Synthesis ◽  
Carbohydrate Oxidation

scholarly journals Quantitative analysis of flux along the gluconeogenic, glycolytic and pentose phosphate pathways under reducing conditions in hepatocytes isolated from fed rats

1983 ◽  
Vol 212 (3) ◽  
pp. 585-598 ◽  
Author(s):  
J M Crawford ◽  
J J Blum
Keyword(s):  
Compartment Model ◽  
Pentose Phosphate ◽  
Improved Method ◽  
Single Compartment ◽  
Reducing Conditions ◽  
Single Compartment Model ◽  
Net Flux ◽  
Pentose Phosphate Pathways ◽  
Fructose 1,6 Bisphosphate ◽  
Hexose Phosphates

Hepatocytes were isolated from the livers of fed rats and incubated with a mixture of glucose (10 mM), ribose (1 mM), mannose (4 mM), glycerol (3 mM), acetate (1.25 mM), and ethanol (5 mM) with one substrate labelled with 14C in any given incubation. Incorporation of label into CO2, glucose, glycogen, lipid glycerol and fatty acids, acetate and C-1 of glucose was measured at 20 and 40 min after the start of the incubation. The data (about 48 measurements for each interval) were used in conjunction with a single-compartment model of the reactions of the gluconeogenic, glycolytic and pentose phosphate pathways and a simplified model of the relevant mitochondrial reactions. An improved method of computer analysis of the equations describing the flow of label through each carbon atom of each metabolite under steady-state conditions was used to compute values for the 34 independent flux parameters in this model. A good fit to the data was obtained, thereby permitting good estimates of most of the fluxes in the pathways under consideration. The data show that: net flux above the level of the triose phosphates is gluconeogenic; label in the hexose phosphates is fully equilibrated by the second 20 min interval; the triose phosphate isomerase step does not equilibrate label between the triose phosphates; substrate cycles are operating at the glucose-glucose 6-phosphate, fructose 6-phosphate-fructose 1,6-bisphosphate and phosphoenolpyruvate-pyruvate-oxaloacetate cycles; and, although net flux through the enzymes catalysing the non-oxidative steps of the pentose phosphate pathway is small, bidirectional fluxes are large.

scholarly journals Rhizobium leguminosarum Biovar viciae 1-Aminocyclopropane-1-Carboxylate Deaminase Promotes Nodulation of Pea Plants

2003 ◽  
Vol 69 (8) ◽  
pp. 4396-4402 ◽  
Author(s):  
Wenbo Ma ◽  
Frèdèrique C. Guinel ◽  
Bernard R. Glick
Keyword(s):  
Pisum Sativum ◽  
Rhizobium Leguminosarum ◽  
Higher Plants ◽  
Regulatory Gene ◽  
Regulatory Protein ◽  
Acc Deaminase ◽  
Ethylene Biosynthesis ◽  
Plant Roots ◽  
Nodule Development ◽  
Insertion Mutants

ABSTRACT Ethylene inhibits nodulation in various legumes. In order to investigate strategies employed by Rhizobium to regulate nodulation, the 1-aminocyclopropane-1-carboxylate (ACC) deaminase gene was isolated and characterized from one of the ACC deaminase-producing rhizobia, Rhizobium leguminosarum bv. viciae 128C53K. ACC deaminase degrades ACC, the immediate precursor of ethylene in higher plants. Through the action of this enzyme, ACC deaminase-containing bacteria can reduce ethylene biosynthesis in plants. Insertion mutants with mutations in the rhizobial ACC deaminase gene (acdS) and its regulatory gene, a leucine-responsive regulatory protein-like gene (lrpL), were constructed and tested to determine their abilities to nodulate Pisum sativum L. cv. Sparkle (pea). Both mutants, neither of which synthesized ACC deaminase, showed decreased nodulation efficiency compared to that of the parental strain. Our results suggest that ACC deaminase in R. leguminosarum bv. viciae 128C53K enhances the nodulation of P. sativum L. cv. Sparkle, likely by modulating ethylene levels in the plant roots during the early stages of nodule development. ACC deaminase might be the second described strategy utilized by Rhizobium to promote nodulation by adjusting ethylene levels in legumes.

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