scholarly journals Plant ribulosamine/erythrulosamine 3-kinase, a putative protein-repair enzyme

2005 ◽  
Vol 388 (3) ◽  
pp. 795-802 ◽  
Author(s):  
Juliette FORTPIED ◽  
Rita GEMAYEL ◽  
Vincent STROOBANT ◽  
Emile van SCHAFTINGEN
Keyword(s):  
Kinase Activity ◽  
Specific Activity ◽  
Calvin Cycle ◽  
Pentose Phosphate ◽  
Leaf Extracts ◽  
Protein Repair ◽  
Spinach Leaf ◽  
Mammalian Enzyme ◽  
Spontaneous Reaction ◽  
Spinach Leaves

FN3K (fructosamine 3-kinase) is a mammalian enzyme that catalyses the phosphorylation of fructosamines, which thereby becomes unstable and detaches from proteins. The homologous mammalian enzyme, FN3K-RP (FN3K-related protein), does not phosphorylate fructosamines but ribulosamines, which are probably formed through a spontaneous reaction of amines with ribose 5-phosphate, an intermediate of the pentose–phosphate pathway and the Calvin cycle. We show in the present study that spinach leaf extracts display a substantial ribulosamine kinase activity (approx. 700 times higher than the specific activity of FN3K in erythrocytes). The ribulosamine kinase was purified approx. 400 times and shown to phosphorylate ribulose-ε-lysine, protein-bound ribulosamines and also, with higher affinity, erythrulose-ε-lysine and protein-bound erythrulosamines. Evidence is presented for the fact that the third carbon of the sugar portion is phosphorylated by this enzyme and that this leads to the formation of unstable compounds decomposing with half-lives of approx. 30 min at 37 °C (ribulosamine 3-phosphates) and 5 min at 30 °C (erythrulosamine 3-phosphates). This decomposition results in the formation of a 2-oxo-3-deoxyaldose and inorganic phosphate, with regeneration of the free amino group. The Arabidopsis thaliana homologue of FN3K/FN3K-RP was overexpressed in Escherichia coli and shown to have properties similar to those of the enzyme purified from spinach leaves. These results indicate that the plant FN3K/FN3K-RP homologue, which appears to be targeted to the chloroplast in many species, is a ribulosamine/erythrulosamine 3-kinase. This enzyme may participate in a protein deglycation process removing Amadori products derived from ribose 5-phosphate and erythrose 4-phosphate, two Calvin cycle intermediates that are potent glycating agents.

THE PHYSIOLOGY OF HOST-PARASITE RELATIONS: IX. FURTHER OBSERVATIONS ON THE ACCUMULATION OF RADIOACTIVE SUBSTANCES AT RUST INFECTIONS

1961 ◽  
Vol 39 (6) ◽  
pp. 1393-1407 ◽  
Author(s):  
Michael Shaw
Keyword(s):  
Specific Activity ◽  
Dry Weight ◽  
Insoluble Fraction ◽  
Pentose Phosphate ◽  
Accumulation Ratio ◽  
X Ray ◽  
Specific Activities ◽  
Leaf Segments ◽  
Wheat Leaves ◽  
Host Parasite

Wang (Can. J. Botany, 38, 635–642 (1960)) concluded that the accumulation of radioactivity observed on radioautographs at infection sites on rusted leaves fed with C14-labelled substances was 'apparent' rather than real. The ‘accumulation ratio’ is defined as the ratio of the specific activities (c.p.m./mg dry weight of intact tissue) of rust-infected to uninfected areas of infected leaves. Theoretical considerations relating to the radioautography of leaves labelled with C14 and to the measurement of ‘accumulation ratios’ by extraction of C14-labelled substances from rusted and uninfected segments of infected leaves, as well as experimental data, show that Wang's conclusion is not generally applicable.Experimentally, it was shown using polymethacrylate C14 sources that differences in distance between sources and X-ray film of the order of 100 μ had no effect on the intensity of autoradiographs. Rust-infected leaves, fed with radioactive glucose, were radiographed between X-ray plates. Localization of radioactivity at infection sites was observed on both ‘dorsal’ and ‘ventral’ radiographs, indicating a real accumulation per unit area. Ventral were more radioactive than dorsal surfaces. The main development of the fungus occurred on the former. Radioautography revealed that C14 from glucose-1-C14, glucose-6-C14, and uniformly labelled glucose fed to excised wheat leaves became localized at 10-day-old rust infections in 2 hours. ‘Accumulation ratios’ calculated from the specific activity of leaf segments remained close to 1.0 for at least 6 hours after introduction of the tracer, but increased to more than 2 after 24 hours. When ‘accumulation ratios’ were calculated from the specific activities of individual pustules (excised with a punch 1 mm in diameter) and interpustular disks, values greater than 1 were observed in 2 hours, thus confirming the results of autoradiography. Differences between the ‘accumulation ratios’ observed with glucose-6-C14 and glucose-1-C14 were consistent with an increased role of the pentose phosphate pathway at infection sites. Incorporation of C14 from uniformly labelled glucose into the alcohol-insoluble fraction of rusted leaf segments was 2.5-fold that in uninfected segments in 6 hours and 3.65-fold in 24 hours. The humin formed during hydrochloric acid hydrolysis accounted for approximately 50% of the activity of the alcohol-insoluble material. The ‘accumulation ratio’ for the alcohol-soluble material was only 1.56 after 24 hours.All the results support the view (Shaw and Samborski, Can. J. Botany, 34, 389–405 (1956)) that there is a quantitative, metabolically dependent accumulation of C14 from radioactive glucose at vigorous rust infections. The relative roles of fungus and host in this process are discussed briefly.

scholarly journals The Saccharomyces cerevisiae YAK1 gene encodes a protein kinase that is induced by arrest early in the cell cycle.

1991 ◽  
Vol 11 (8) ◽  
pp. 4045-4052 ◽  
Author(s):  
S Garrett ◽  
M M Menold ◽  
J R Broach
Keyword(s):  
Cell Cycle ◽  
Protein Kinase ◽  
Kinase Activity ◽  
Specific Activity ◽  
S Phase ◽  
Protein Kinase Activity ◽  
Dependent Protein Kinase ◽  
Protein Levels ◽  
Cycle Arrest ◽  
Dependent Protein

Null mutations in the gene YAK1, which encodes a protein with sequence homology to known protein kinases, suppress the cell cycle arrest phenotype of mutants lacking the cyclic AMP-dependent protein kinase (A kinase). That is, loss of the YAK1 protein specifically compensates for loss of the A kinase. Here, we show that the protein encoded by YAK1 has protein kinase activity. Yak1 kinase activity is low during exponential growth but is induced at least 50-fold by arrest of cells prior to the completion of S phase. Induction is not observed by arrest at stages later in the cell cycle. Depending on the arrest regimen, induction can occur either by an increase in Yak1 protein levels or by an increase in Yak1 specific activity. Finally, an increase in Yak1 protein levels causes growth arrest of cells with attenuated A kinase activity. These results suggest that Yak1 acts in a pathway parallel to that of the A kinase to negatively regulate cell proliferation.

Chloroplast division in spinach leaves examined by scanning electron microscopy and freeze-etching

1980 ◽  
Vol 46 (1) ◽  
pp. 87-96
Author(s):  
N. Chaly ◽  
J.V. Possingham ◽  
W.W. Thomson
Keyword(s):  
Electron Microscopy ◽  
Green Light ◽  
Cell Area ◽  
Low Intensity ◽  
Spinach Leaf ◽  
Freeze Etching ◽  
Leaf Disks ◽  
Scanning Electron ◽  
Spinach Leaves

Spinach leaf disks were cultured for 5 days in low-intensity green light and then were transferred to high-intensity white light. Harvests over the next 16 h established that cell area increased by about 80% and chloroplast number per cell increased by about 65%, while the percentage of dumbbell-shaped chloroplasts per cell decreased by 65%. Freeze-etch replicas of fixed and unfixed leaf disks, as well as scanning electron-microscope preparations of fixed material, contained dumbbell-shaped chloroplasts constricted to various degrees. Freeze-etch replicas of unfixed cells from young leaf bases, in which the number of chloroplasts per cell is known to be rapidly increasing, also contained many constricted chloroplasts. It is concluded that dumbbell-shaped chloroplasts occur in vivo and represent a stage in the division of chloroplasts.

scholarly journals Functional analysis of the biochemical activity of mammalian phosphatidylinositol 5 phosphate 4-kinase enzymes

2019 ◽  
Vol 39 (2) ◽  
Author(s):  
Swarna Mathre ◽  
K. Balasankara Reddy ◽  
Visvanathan Ramya ◽  
Harini Krishnan ◽  
Avishek Ghosh ◽  
...  
Keyword(s):  
Salivary Gland ◽  
Cell Size ◽  
Kinase Activity ◽  
Gland Cell ◽  
Specific Activity ◽  
Salivary Gland Cell ◽  
Drosophila Genome ◽  
Biochemical Activity

Abstract Phosphatidylinositol 5 phosphate 4-kinase (PIP4K) are enzymes that catalyse the phosphorylation of phosphatidylinositol 5-phosphate (PI5P) to generate PI(4,5)P2. Mammalian genomes contain three genes, PIP4K2Α, 2B and 2C and murine knockouts for these suggested important physiological roles in vivo. The proteins encoded by PIP4K2A, 2B and 2C show widely varying specific activities in vitro; PIP4K2A is highly active and PIP4K2C 2000-times less active, and the relationship between this biochemical activity and in vivo function is unknown. By contrast, the Drosophila genome encodes a single PIP4K (dPIP4K) that shows high specific activity in vitro and loss of this enzyme results in reduced salivary gland cell size in vivo. We find that the kinase activity of dPIP4K is essential for normal salivary gland cell size in vivo. Despite their highly divergent specific activity, we find that all three mammalian PIP4K isoforms are able to enhance salivary gland cell size in the Drosophila PIP4K null mutant implying a lack of correlation between in vitro activity measurements and in vivo function. Further, the kinase activity of PIP4K2C, reported to be almost inactive in vitro, is required for in vivo function. Our findings suggest the existence of unidentified factors that regulate PIP4K enzyme activity in vivo.

A Possible Mechanism for a Light-Driven Regulation of the Fatty Acid Composition in Galactolipids of Chloroplasts

1979 ◽  
Vol 34 (9-10) ◽  
pp. 815-819
Author(s):  
A. Sauer ◽  
K .-P. Heise
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Unsaturated Fatty Acids ◽  
Specific Activity ◽  
Physiological State ◽  
Phospholipid Fraction ◽  
Chromatographic Behavior ◽  
Acyl Acceptor ◽  
Lipid Mixture ◽  
Spinach Leaves

Abstract The occurrence of acylgalactosylglycerol (AGG) in spinach chloroplasts is proposed. In lipid se­parations of whole spinach leaves this fraction is hidden by variable amounts of extraplastidary steryl glucoside (SG) which depended on the physiological state of the leaf material. Beside the phospholipid fraction, this lipid mixture with unique chromatographic behavior, recently termed GL, exhibited the highest specific activity in the lipid extract of infiltrated leaf sections of spinach after short periods of illumination (2 min) under 14C-fixing conditions. The main source of label was found in the fatty acid residues of the lipids described. The decrease of specific activity in GL after a cold chase was accompanied by an increasing 14C-incorporation into the fatty acid moieties of the MGDG-as well as the phospholipid fraction. This effect was significantly reduced if the 14C-pulse was followed by a dark period. This incorporation behavior suggests, that AGG functions as an intermediary acyl acceptor in the light driven fatty acid transfer between the lipids decribed. SG-synthesis, on the contrary, is independent of additional illumination and seems to be localized outside the chloroplast. The last notion was derived from experiments involving the in­ corporation of [UDP-14C] glucose into SG by spinach leaf homogenates. With regard to the increasing level of trienoic fatty acids in AGG and MGDG during the regeneration of dark pretreated spinach leaves in the light, the data are interpreted in terms of a light regulated acylation of AGG with specific unsaturated fatty acids.

scholarly journals Analysis of Proximate Composition and Functional Properties of Selected Edible Leaves: Nutritional and Therapeutic Implication

2020 ◽  
Vol 12 (4) ◽  
pp. 621-632
Author(s):  
A. D. Pal ◽  
T. M. Zakir
Keyword(s):  
Functional Properties ◽  
Local Population ◽  
Antioxidant Properties ◽  
Reducing Power ◽  
Good Health ◽  
Proximate Analysis ◽  
Leaf Extracts ◽  
Therapeutic Benefits ◽  
Spinach Leaves

The present study was designed to document the nutritional and functional properties of Ceylon Spinach, Mustard as well as Pumpkin leaves. These samples were selected owing to their economic affordability and utilization within the local population. Proximate analysis revealed a significant percentage of minerals, proteins, carbohydrates and vitamin C in all the leaf extracts. Phytochemical screening displayed Ceylon Spinach, Pumpkin and Mustard leaves to be rich sources of polyphenols (106.6, 76.24 and 89.86 mg/100 g) and alkaloids (12.8 %, 13.2 % and 16.8 %) respectively. Furthermore, these edible leaves could effectively scavenge 2, 2-diphenyl-1-picryl-hydrazyl (DPPH) and hydrogen peroxide (H2O2) free radicals with Mustard leaves showing the greatest efficiency, hence portraying antioxidant properties. Ceylon Spinach leaves depicted the highest reducing power compared to the other samples. Additionally, the edible leaf extracts were shown to possess anti-bacterial abilities with Mustard leaves displaying the strongest inhibition against growth of both Gram positive (ZOI 18.5mm) and negative bacteria (ZOI 25.5mm). Interestingly, the selected samples could also elevate the growth of probiotic Lactobacillus acidophilus in vitro thereby confirming their prebiotic potential. Therefore, inclusion of these edible leaves in the diet may promote good health owing to their nutritional and therapeutic benefits.

INFLUENCE OF SEX HORMONES ON AMIDINOTRANSFERASE LEVELS. METABOLIC CONTROL OF CREATINE BIOSYNTHESIS

1966 ◽  
Vol 53 (4) ◽  
pp. 655-662 ◽  
Author(s):  
István Kriskó ◽  
James B. Walker
Keyword(s):  
Testosterone Propionate ◽  
De Novo ◽  
Specific Activity ◽  
Hormonal Control ◽  
Mature Male ◽  
Female Rats ◽  
Male Rats ◽  
Enzyme Protein ◽  
Wet Weight ◽  
Mammalian Enzyme

ABSTRACT Arginine: glycine amidinotransferase is the first of two enzymes involved in creatine biosynthesis. The amidinotransferase specific activity (micromoles of hydroxyguanidine formed per hour per g wet weight of tissue) of kidney homogenates of mature male rats was about twice that of females of the same age, whereas activities were equal before puberty. Castration decreased the activity of males and increased that of females. The administration of testosterone propionate to young adult female rats resulted in a significant increase in enzyme activity. The same enzyme had previously been shown to be repressible by its end-product, creatine. Although there are numerous enzymes whose synthesis is known to be under hormonal control, amidinotransferase is the only mammalian enzyme described up to now on which there appears to operate both an end-product repression mechanism and a hormonal control on the de novo synthesis of the enzyme protein.

Rubisco Activase Activity in Spinach Leaf Extracts

1995 ◽  
Vol 36 (2) ◽  
pp. 215-220 ◽  
Author(s):  
William J. Campbell ◽  
William L. Ogren
Keyword(s):  
Rubisco Activase ◽  
Leaf Extracts ◽  
Spinach Leaf

scholarly journals Mammary tumors expressing the neu proto-oncogene possess elevated c-Src tyrosine kinase activity.

1994 ◽  
Vol 14 (1) ◽  
pp. 735-743 ◽  
Author(s):  
S K Muthuswamy ◽  
P M Siegel ◽  
D L Dankort ◽  
M A Webster ◽  
W J Muller
Keyword(s):  
Signal Transduction ◽  
Tyrosine Kinase ◽  
Kinase Activity ◽  
Specific Activity ◽  
Fusion Gene ◽  
Mammary Tumorigenesis ◽  
Mammary Tumors ◽  
Tyrosine Kinase Activity ◽  
Src Tyrosine Kinase

Amplification and overexpression of the neu (c-erbB2) proto-oncogene has been implicated in the pathogenesis of 20 to 30% of human breast cancers. Although the activation of Neu receptor tyrosine kinase appears to be a pivotal step during mammary tumorigenesis, the mechanism by which Neu signals cell proliferation is unclear. Molecules bearing a domain shared by the c-Src proto-oncogene (Src homology 2) are thought to be involved in signal transduction from activated receptor tyrosine kinases such as Neu. To test whether c-Src was implicated in Neu-mediated signal transduction, we measured the activity of the c-Src tyrosine kinase in tissue extracts from either mammary tumors or adjacent mammary epithelium derived from transgenic mice expressing a mouse mammary tumor virus promoter/enhancer/unactivated neu fusion gene. The Neu-induced mammary tumors possessed six- to eightfold-higher c-Src kinase activity than the adjacent epithelium. The increase in c-Src tyrosine kinase activity was not due to an increase in the levels of c-Src but rather was a result of the elevation of its specific activity. Moreover, activation of c-Src was correlated with its ability to complex tyrosine-phosphorylated Neu both in vitro and in vivo. Together, these observations suggest that activation of the c-Src tyrosine kinase during mammary tumorigenesis may occur through a direct interaction with activated Neu.

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