The Interaction of Mercuric Acetate with Indoles, Tryptophan, and Proteins

Ramachandran, L. K.; Witkop, Bernhard

doi:10.1021/bi00899a001

Cited by 49 publications

(9 citation statements)

References 16 publications

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“…Enzyme activity was inhibited by several of the compounds tested. Inhibition by mercuric ions may indicate the importance of indole amino acids in enzyme function (27), as has been demonstrated for a Penicillium cellulase (5). N-Bromosuccinimide has several modification functions; among these are reactivity with tyrosine, histidine, tryptophan, thiol, and disulfide groups (45) and cleavage of proteins (13).…”

Section: Appl Environ Microbiolmentioning

confidence: 88%

Purification and Characterization of an Endo-(1,3)-β- d -Glucanase from Trichoderma longibrachiatum

Tangarone

Royer

Nakas

1989

Appl Environ Microbiol

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A laminarinase [endo-(1,3)-p-D-glucanasel has been purified from Trichoderma longibrachiatum cultivated with D-glucose as the growth substrate. The enzyme was found to hydrolyze laminarin to oligosaccharides varying in size from glucose to pentaose and to lesser amounts of larger oligosaccharides. The enzyme was unable to cleave laminaribiose but hydrolyzed triose to laminaribiose and glucose. The enzyme cleaved laminaritetraose, yielding laminaritriose, laminaribiose, and glucose, and similarly cleaved laminaripentaose, yielding laminaritetraose, laminaritriose, laminaribiose, and glucose. The enzyme cleaved only glucans containing 0-1,3 linkages. The pH and temperature optima were 4.8 and 55°C, respectively. Stability in the absence of a substrate was observed at temperatures up to 50°C and at pH values between 4.9 and 9.3. The molecular mass was determined to be 70 kilodaltons by sodium dodecyl sulfate-12.5% polyacrylamide gel electrophoresis, and the pl was 7.2. Enzyme activity was significantly inhibited in the presence of HgCl2, MnCl2, KMnO4, and N-bromosuccinimide. The Km of the enzyme on laminarin was 0.0016%, and the Vmax on laminarin was 3,170 ,umol of glucose equivalents per mg of the pure enzyme per min.

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Section: Appl Environ Microbiolmentioning

confidence: 88%

Purification and Characterization of an Endo-(1,3)-β- d -Glucanase from Trichoderma longibrachiatum

Tangarone

Royer

Nakas

1989

Appl Environ Microbiol

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“…During measurement of Nat-dependent transport of AIB, 10 mM tryptophan was present to inhibit uptake by the Na+-independent system L transporter (Brookes, 1988~). Because it was conceivable that tryptophan might modify the response to HgC12 (Ramachandran and Witkop, 1964), inhibition of the uptake of glutamate (100 pM, 8 min) by 1 pM HgC12 was measured in the presence and absence of 10 mM tryptophan. However, the percentages of control glutamate uptake were 18.9 L 5.5 (mean It_ SD; n = 3) and 3 1.2 k 6.3, respectively, which are not statistically different.…”

Section: Initial Velocity Of Amino Acid Uptakementioning

confidence: 99%

Inhibition of Amino Acid Transport and Protein Synthesis by HgCl₂ and Methylmercury in Astrocytes: Selectivity and Reversibility

Brookes¹,

Kristt

1989

Journal of Neurochemistry

107

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The previously reported observation that submicromolar concentrations of HgCl2 inhibit glutamate uptake reversibly in astrocytes, without effect on 2-deoxyglucose uptake, suggested that elemental mercury vapor, which is oxidized to mercuric mercury in the brain, might cause neurodegenerative change through the mediation of glutamate excitotoxicity. Here, selectivity is explored further by measuring the inhibition of other amino acid transporters and protein synthesis as a function of HgCl2 concentration. The properties of MeHgCl were compared under identical conditions, and some morphological correlates of function were examined. Inhibition of amino acid transport by HgCl2 was selective, whereas MeHgCl was nonselective. The 50% inhibitory concentrations of HgCl2 for uptake of alpha-aminoisobutyric acid by system A, uptake of alpha-aminoisobutyric acid or kynurenine by a system L variant, and uptake of gamma-aminobutyric acid were all two- to fourfold greater than that for uptake of glutamate. The submicromolar concentrations of HgCl2 that inhibited glutamate transport also inhibited protein synthesis, but in a rapidly reversible fashion, and elicited only discrete ultrastructural changes (heterochromatin, increased numbers of lysosomal bodies, and increased complexity of cell surface). In contrast, inhibition of protein synthesis by MeHgCl was acutely (1-h) irreversible and became marked only at concentrations higher than those that elicited gross morphologic change in the form of "bleb"-like swellings. The results lend support to the proposed excitotoxic mediation of mercury vapor neurotoxicity and reveal a sharp contrast between the effects of HgCl2 and MeHgCl on astrocytes.

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“…Mercurials form stable complexes with a variety of chemical groups found in membranes [1,19,28], for example: -SH groups, unsaturated double bonds of lipids and tryptophan, aromatic rings, carboxyl groups, terminal amines, and imidazole of histidine. With few exceptions [1,25], inhibition of protein function can be linked to reactions with sulfhydryl groups~ The present study does not offer any direct evidence bearing on this question.…”

Section: Model Of Irreversible Inhibitionmentioning

confidence: 99%

Mercurial perturbation of brush border membrane permeability in rabbit ileum

Stirling

1975

J. Membrain Biol.

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The sulfhydryl reagents Hg++ and p-chloromercuribenzene sulfonate (PCMBS) at millimolar concentrations reduced the mucosal entry of sugars and amino acids to 80-90% of control levels within several minutes. Based on 50% levels of inhibition, Hg++ proved to be 20 and 10 times as potent as PCMBS in blocking sugar and amino acid transport, respectively; both systems were equally sensitive to Hg++. Concomitant measurements of 203Hg-PCMBS demonstrated a progressive tissue uptake, which, unlike inhibition, did not saturate with increasing times of exposure, thus suggesting appreciable epithelial entry with prolonged exposures (less than 30 min at 1 mM). At similar dose levels, no significant change in mucosal Na+ entry was detected. Inhibition was not reversed by 30-min washes in cholinesalt solutions; however, 10-min exposures to dithiothreitol [10 mM] reversed Hg++ and PCMBS inhibition by 40 and 100%, respectively. Alanine and galactose influx kinetics measured at concentrations of 0-100 mM exhibited a linear or diffusional entry component in addition to the usual saturable component for both control and Hg++-treated ileum. The presence of a diffusional term in the flux equation resulted in two sets of parameters giving nearly equal fits to these measurements. It was shown that this ambiguity could be resolved by determining the change in diffusional entry with Hg++ treatment. A 20-min exposure to 0.5 mM Hg++ caused an increase from 0.050 and 0.045 to 0.064 and 0.070 cm/hr in the coefficient of diffusional entry for alanine and galactose, respectively. On the basis of this increase, it is argued that Hg++ causes a decrease in Jmax and little change in Km for both transport mechanisms. This analysis has a general bearing on kinetic measurements of transport in which passive fluxes are comparable to those mediated by specific pathways. The alanine results are consistent with bimolecular reactions between mercurial and two membrane inhibitory sites, each producing approximately 40% reduction in membrane translocation rate. The estimated reaction rate constants were 5.0 and 0.4 mM min.

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The Interaction of Mercuric Acetate with Indoles, Tryptophan, and Proteins

Cited by 49 publications

References 16 publications

Purification and Characterization of an Endo-(1,3)-β- d -Glucanase from Trichoderma longibrachiatum

Purification and Characterization of an Endo-(1,3)-β- d -Glucanase from Trichoderma longibrachiatum

Inhibition of Amino Acid Transport and Protein Synthesis by HgCl₂ and Methylmercury in Astrocytes: Selectivity and Reversibility

Mercurial perturbation of brush border membrane permeability in rabbit ileum

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The Interaction of Mercuric Acetate with Indoles, Tryptophan, and Proteins

Cited by 49 publications

References 16 publications

Purification and Characterization of an Endo-(1,3)-β- d -Glucanase from Trichoderma longibrachiatum

Purification and Characterization of an Endo-(1,3)-β- d -Glucanase from Trichoderma longibrachiatum

Inhibition of Amino Acid Transport and Protein Synthesis by HgCl2 and Methylmercury in Astrocytes: Selectivity and Reversibility

Mercurial perturbation of brush border membrane permeability in rabbit ileum

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Inhibition of Amino Acid Transport and Protein Synthesis by HgCl₂ and Methylmercury in Astrocytes: Selectivity and Reversibility