Molecular Mechanism for the α-Glucosidase Inhibitory Effect of Wheat Germ Peptides

During the sexual cycle of Dictyostelium discoideum, zygote giant cells develop and serve as foci for further development by chemoattracting and cannibalizing hundreds of local amoebae. Previous work has shown that the phagocytic process bears similarities to and differences from asexual endocytosis. In the present study, sexual phagocytosis in D. discoideum was found to be species and developmental stage specific. It was inhibited selectively by glucose and concanavalin A. Although a partial, inhibitory effect of mannose on phagocytosis was not statistically significant, alpha-methylmannosamine, like alpha-methyl-glucose, significantly restored the phagocytic competence of giant cells treated with concanavalin A. Other sugars (N-acetyl glucosamine, N-acetylgalactosamine, and galactose) and lectins (wheat germ agglutinin, Ulex europus type I, and Ricinis communis agglutinin type I) had no significant effect on sexual phagocytosis. Together these data indicate that a glucose-type receptor is involved in selective uptake of D. discoideum amoebae by giant cells.

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Receptor-mediated gonadotropin action in the ovary. Inhibitory actions of concanavalin A and wheat-germ agglutinin on gonadotropin-stimulated cyclic AMP and progesterone responses in ovarian cells

Biochemical Journal ◽

10.1042/bj2000153 ◽

1981 ◽

Vol 200 (1) ◽

pp. 153-159 ◽

Cited By ~ 3

Author(s):

S Azhar ◽

K M Menon

Keyword(s):

Cyclic Amp ◽

Concanavalin A ◽

Wheat Germ Agglutinin ◽

Wheat Germ ◽

Carbohydrate Chain ◽

Inhibitory Effect ◽

Dolichos Biflorus ◽

Acetylneuraminic Acid ◽

Ovarian Cells ◽

Proline Incorporation

Pretreatment of ovarian cells with concanavalin A and wheat-germ agglutinin blocked the gonadotropin-induced cyclic AMP and progesterone responses and this effect was time- and concentration-dependent. Basal production of either cyclic AMP or progesterone, however, was not affected by treatment of cells with lectin. The effect of concanavalin A on gonadotropin-mediated cyclic AMP and progesterone responses was blocked by alpha-methyl D-mannoside and alpha-methyl d-glucoside. Similarly the inhibitory effect of wheat-germ agglutinin was reversed by N-acetyl-D-glucosamine. Pretreatment of ovarian cells with concanavalin A or wheat-germ agglutinin had no effect on protein synthesis in the ovary as monitored by [3H]proline incorporation studies. Concanavalin A and wheat-germ agglutinin did not affect steroid production in response to dibutyryl cyclic AMP and 8-bromo cyclic AMP, indicating that the inhibitory action of lectin was occurring at a step before cyclic AMP formation. Lectins specific for L-fucose, D-galactose and N-acetyl-D-galactosamine, gorse seed agglutinin, peanut agglutinin and Dolichos biflorus agglutinin respectively, did not interfere with gonadotropin-induced cyclic AMP and progesterone responses. The present studies suggest that gonadotropin receptors may be glycoprotein in nature or closely associated with glycoprotein structures with the carbohydrate chain containing N-acetyl-D-glucosamine, mannose and possibly N-acetylneuraminic acid.

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Urea inhibits hypertonicity-inducible TonEBP expression and action

AJP Renal Physiology ◽

10.1152/ajprenal.2001.280.5.f904 ◽

2001 ◽

Vol 280 (5) ◽

pp. F904-F912 ◽

Cited By ~ 16

Author(s):

Wei Tian ◽

David M. Cohen

Keyword(s):

Transcription Factor ◽

Molecular Mechanism ◽

Reporter Gene ◽

Gene Transcription ◽

Phorbol Ester ◽

Renal Medulla ◽

Inhibitory Effect ◽

Characteristic Set ◽

Enhancer Element ◽

Enhancer Binding Protein

Tonicity-responsive genes are regulated by the TonE enhancer element and the tonicity-responsive enhancer binding protein (TonEBP) transcription factor with which it interacts. Urea, a permeant solute coexistent with hypertonic NaCl in the mammalian renal medulla, activates a characteristic set of signaling events that may serve to counteract the effects of NaCl in some contexts. Urea inhibited the ability of hypertonic stressors to increase expression of TonEBP mRNA and also inhibited tonicity-inducible TonE-dependent reporter gene activity. The permeant solute glycerol failed to reproduce these effects, as did cell activators including peptide mitogens and phorbol ester. The inhibitory effect of urea was evident as late as 2 h after the application of hypertonicity. Pharmacological inhibitors of known urea-inducible signaling pathways failed to abolish the inhibitory effect of urea. TonEBP action is incompletely understood, but evidence supports a role for proteasome function and p38 action in regulation; urea failed to inhibit proteasome function or p38 signaling in response to hypertonicity. Consistent with its effect on TonEBP expression and action, urea pretreatment inhibited the effect of hypertonicity on expression of the physiological effector gene, aldose reductase. Taken together, these data 1) define a molecular mechanism of urea-mediated inhibition of tonicity-dependent signaling, and 2) underscore a role for TonEBP abundance in regulating TonE-mediated gene transcription.

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The molecular mechanism of fullerene-inhibited aggregation of Alzheimer's β-amyloid peptide fragment

Nanoscale ◽

10.1039/c4nr01005a ◽

2014 ◽

Vol 6 (16) ◽

pp. 9752-9762 ◽

Cited By ~ 75

Author(s):

Luogang Xie ◽

Yin Luo ◽

Dongdong Lin ◽

Wenhui Xi ◽

Xinju Yang ◽

...

Keyword(s):

Molecular Mechanism ◽

Inhibitory Effect ◽

Amyloid Peptide ◽

Peptide Fragment ◽

Experiment Study ◽

Simulation And Experiment ◽

Β Amyloid ◽

Combined Simulation ◽

Β Amyloid Peptide ◽

Β Sheet

A combined simulation and experiment study demonstrates that fullerenes inhibit the β-sheet formation of Aβ(16–22) and fullerene hexagonal rings play a significant role on the inhibitory effect.

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Phenylalanine Analogues: Potent Inhibitors of Phenylalanine Ammonia-Lyase Are Weak Inhibitors of Phenylalanine-tRNA Synthetases

Zeitschrift für Naturforschung C ◽

10.1515/znc-1994-11-1214 ◽

1994 ◽

Vol 49 (11-12) ◽

pp. 781-790 ◽

Cited By ~ 6

Author(s):

Gerhard Leubner Metzger ◽

Nikolaus Amrhein

Keyword(s):

Wheat Germ ◽

Phenylalanine Ammonia Lyase ◽

Inhibitory Effect ◽

Baker’S Yeast ◽

Baker's Yeast ◽

Exchange Reactions ◽

Trna Synthetases ◽

Different Sources

(1-Amino-2-phenylethyl)phosphonic acid (APEP), (1-amino-2-phenylethyl)phosphonous acid (APEPi), α-aminooxy-β-phenylpropionic acid (AOPP) and several other phenylalanine analogues are potent inhibitors of (S)-phenylalanine ammonia-lyase (PAL) in vitro and in vivo. The ability of these compounds to inhibit (S)-phenylalanine-tRNA synthetases (PRSs) from wheat germ, soybean, and baker’s yeast has been investigated and compared to the inhibition of PAL. APEP and APEPi were found to inhibit the tRNAphe-aminoacylation reactions catalyzed by the three PRSs studied in vitro in a competitive manner with respect to (5)-phenylalanine. (R)-APEP inhibits the PRSs with apparent Ki values of 144 μᴍ for wheat germ (app. Km for (S)-phe 5.2 μᴍ) , 130 μᴍ for soybean (app. Km for (S)-phe 0.9 μᴍ) , and 1096 μᴍ for baker’s yeast (app. Km for (S)-phe 5.5 μᴍ ) . The apparent Ki values for (R)-APEPi are 315 μᴍ , 160 μᴍ , and 117 μᴍ , respectively. APEP and APEPi inhibit the ATPpyrophosphate exchange reactions catalyzed by the PRSs from wheat germ and baker’s yeast, but they are not activated and do not serve as substrates in these reactions. AOPP has no affinity to any of the three PRSs, whereas it is a potent inhibitor of PAL. In light of our in vitro results with PRSs from different sources it appears unlikely that the PAL inhibitors we have studied have any significant inhibitory effect on this essential step in protein synthesis in vivo.

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