The Experts below are selected from a list of 72 Experts worldwide ranked by ideXlab platform

Kather H - One of the best experts on this subject based on the ideXlab platform.

  • Human fat cells possess a plasma membrane-bound H2O2-generating system that is activated by insulin via a mechanism bypassing the receptor kinase.
    1992
    Co-Authors: Krieger-brauer H, Kather H
    Abstract:

    Insulin caused a transient increase in H2O2 accumulation in human fat cell suspensions that was observed only in the presence of an inhibitor of catalase and heme-containing peroxidases, such as azide, and reached peak levels of 30 microM within 5 min. The cells contained a plasma membrane-bound NADPH oxidase, producing 1 mol H2O2/mol of NADPH oxidation, that was activated on exposure of intact cells to insulin at contrations that are physiologically relevant (0.1-10 nM). The hormone effect was rapid and was due to a selective increase in substrate affinity. The enzyme was magnesium dependent, required a Flavine Nucleotide for optimal activity, and was most active at pH 5.0-6.5. In contrast to all other hormone- or cytokine-sensitive NADPH oxidases that have been characterized in sufficient detail, the human fat cell oxidase retained its hormone responsiveness after cell disruption, and only Mn2+, but no ATP, was required for a ligand-induced activation in crude plasma membranes. The results demonstrate that insulin utilizes tyrosine kinase-independent pathways for receptor signaling and strongly support the view that H2O2 contributes to the intracellular propagation of the insulin signal

H Kather - One of the best experts on this subject based on the ideXlab platform.

  • Human fat cells possess a plasma membrane-bound H2O2-generating system that is activated by insulin via a mechanism bypassing the receptor kinase.
    The Journal of clinical investigation, 1992
    Co-Authors: H I Krieger-brauer, H Kather
    Abstract:

    Insulin caused a transient increase in H202 accumulation in human fat cell suspensions that was observed only in the presence of an inhibitor of catalase and heme-containing peroxidases, such as azide, and reached peak levels of30gM within 5 min. The cells contained a plasma membrane-bound NADPH oxidase, producing 1 mol H202/mol ofNADPH oxidation, that was activated on exposure of intact cells to insulin at contrations that are physiologically relevant (0.1-10 nM). The hormone effect was rapid and was due to a selective increase in substrate affinity. The enzyme was magnesium dependent, required a Flavine Nucleotide for optimal activity, and was most active at pH 5.0-6.5. In contrast to all other hormone- or cytokine-sensitive NADPH oxidases that have been characterized in sufficient detail, the human fat cell oxidase retained its hormone responsiveness after cell disruption, and only Mn2', but no ATP, was required for a ligand-induced activation in crude plasma membranes. The results demonstrate that insulin utilizes tyrosine kinase-independent pathways for receptor signaling and strongly support the view that H202 contributes to the intracellular propagation of the insulin signal. (J. Clin. Invest.

Krieger-brauer H - One of the best experts on this subject based on the ideXlab platform.

  • Human fat cells possess a plasma membrane-bound H2O2-generating system that is activated by insulin via a mechanism bypassing the receptor kinase.
    1992
    Co-Authors: Krieger-brauer H, Kather H
    Abstract:

    Insulin caused a transient increase in H2O2 accumulation in human fat cell suspensions that was observed only in the presence of an inhibitor of catalase and heme-containing peroxidases, such as azide, and reached peak levels of 30 microM within 5 min. The cells contained a plasma membrane-bound NADPH oxidase, producing 1 mol H2O2/mol of NADPH oxidation, that was activated on exposure of intact cells to insulin at contrations that are physiologically relevant (0.1-10 nM). The hormone effect was rapid and was due to a selective increase in substrate affinity. The enzyme was magnesium dependent, required a Flavine Nucleotide for optimal activity, and was most active at pH 5.0-6.5. In contrast to all other hormone- or cytokine-sensitive NADPH oxidases that have been characterized in sufficient detail, the human fat cell oxidase retained its hormone responsiveness after cell disruption, and only Mn2+, but no ATP, was required for a ligand-induced activation in crude plasma membranes. The results demonstrate that insulin utilizes tyrosine kinase-independent pathways for receptor signaling and strongly support the view that H2O2 contributes to the intracellular propagation of the insulin signal

H I Krieger-brauer - One of the best experts on this subject based on the ideXlab platform.

  • Human fat cells possess a plasma membrane-bound H2O2-generating system that is activated by insulin via a mechanism bypassing the receptor kinase.
    The Journal of clinical investigation, 1992
    Co-Authors: H I Krieger-brauer, H Kather
    Abstract:

    Insulin caused a transient increase in H202 accumulation in human fat cell suspensions that was observed only in the presence of an inhibitor of catalase and heme-containing peroxidases, such as azide, and reached peak levels of30gM within 5 min. The cells contained a plasma membrane-bound NADPH oxidase, producing 1 mol H202/mol ofNADPH oxidation, that was activated on exposure of intact cells to insulin at contrations that are physiologically relevant (0.1-10 nM). The hormone effect was rapid and was due to a selective increase in substrate affinity. The enzyme was magnesium dependent, required a Flavine Nucleotide for optimal activity, and was most active at pH 5.0-6.5. In contrast to all other hormone- or cytokine-sensitive NADPH oxidases that have been characterized in sufficient detail, the human fat cell oxidase retained its hormone responsiveness after cell disruption, and only Mn2', but no ATP, was required for a ligand-induced activation in crude plasma membranes. The results demonstrate that insulin utilizes tyrosine kinase-independent pathways for receptor signaling and strongly support the view that H202 contributes to the intracellular propagation of the insulin signal. (J. Clin. Invest.

Parham Rami - One of the best experts on this subject based on the ideXlab platform.

  • Localization, biochemical characterization, and solubilization of (4-vinyl) chlorophyllide a reductase, a novel chlorophyll a biosynthetic enzyme
    1
    Co-Authors: Parham Rami
    Abstract:

    (4-vinyl) chlorophyllide a reductase (4VCR), catalyses the conversion of divinyl chlorophyllide a (DVChlide a) to monovinyl chlorophyllide a (MVChlide a). The latter is the immediate precursor of monovinyl chlorophyll a (MVChl a) in plants and algae. In reaction center and light harvesting pigment-protein complexes, MVChl a is the main, photosynthetically active protein.4VCR has been localized in membrane fractions of plastids isolated from etiolated cucumber (Cucumis sativus L.) cotyledons. The enzyme has also been detected in two monocotyledonous species, namely corn (Zea mays L.), and barley (Hordeum vulgare L.). In these species, 4VCR activity has been shown to be maximal in etiolated tissues and drop sharply upon illumination. 4VCR requires the reducing power NADPH as source or hydride ion. Neither a metal ion, nor any cofactor requirement, other than NADPH, could be demonstrated for 4VCR activity. The latter has been shown to be optimal at 30$\sp\circ$C, pH 6.3. Michaelis-Menten constants for DVChlide a and NADPH have been determined to be respectively 0.09-2.00 $\mu$M, and 1.1 mM. 4VCR's low Km value for DVChlide a, in parallel with substrate specificity studies suggested that the enzyme is highly specific for DVChlide a and not other, early and late, divinyl intermediates. The narrow substrate specificity of this bridge-enzyme contrasts with the broad specificity of the forward enzymes of the pathway. The diphenyl ether herbicide acifluorfen methyl (AFM), and the photodynamic herbicide modulator 1, 10-phenanthroline (OPh), inhibited 4VCR activity with respective Ki values of 0.86 and 1.47 mM. The structural requirements of this inhibition have been demonstrated to lie on the presence of at least one nitrogen in a 3-ring, heterocyclic, phenanthroline-related inhibitor. Moreover, electrostatic interactions involving the fractional charge at position 7 of the inhibitor heterocycle appear to be at play in the binding of the inhibitor to the enzyme. Preliminary structural studies of the enzyme have revealed the presence of free, and accessible cystein residues, essential for enzyme activity. Finally, strong inhibition caused by the Flavine antagonist quinacrine, suggested that a Flavine Nucleotide may be involved in the transfer of the hydride from NADPH to DVChlide a.U of I OnlyETDs are only available to UIUC Users without author permissio