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Galactoside

About: Galactoside is a(n) research topic. Over the lifetime, 662 publication(s) have been published within this topic receiving 15406 citation(s). The topic is also known as: galactosides.

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Journal ArticleDOI
Hans Winkler1, T H Wilson1Institutions (1)
TL;DR: Evidence was consistent with the hypothesis that the same membrane carriers were involved in active transport by control cells and facilitated diffusion by poisoned cells, and the most striking finding was that the addition of metabolic inhibitors reduced the KT of exit about two orders of magnitude, whereas the Kt of entrance remained constant.

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Abstract: Lactose and o-nitrophenylgalactoside (NPG) were transported against considerable concentration gradients by ML 308-225, a mutant of Escherichia coli which lacks β-galactosidase but possesses a constitutive transport system for β-galactosides. The kinetics of influx of NPG during this accumulation were found to be the same as those found for this galactoside moving down a concentration gradient into ML 308, i.e. transport into the parent cell containing β-galactosidase. When cells of ML 308-225 were exposed to azide, azide plus iodoacetate, or dinitrophenol transport of these galactosides against a concentration gradient was completely abolished. However, the presence of functional membrane carriers in such inhibited cells was indicated by (a) very rapid equilibration of external and internal concentrations of galactoside, (b) inhibition of the rate of this equilibration by chemical analogues, and (c) transientaccumulation of substrate by washed cells preloaded with galactoside. All the evidence was consistent with the hypothesis that the same membrane carriers were involved in active transport by control cells and facilitated diffusion by poisoned cells. The most striking finding was that the addition of metabolic inhibitors reduced the Kt of exit about two orders of magnitude, whereas the Kt of entrance remained constant. It was inferred from these studies that energy coupling reduced the affinity of the carrier for its substrate on the inner surface of the plasma membrane. The possible physiological control of energy coupling of transport was discussed in the light of the present observations.

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387 citations


Journal ArticleDOI
25 Mar 1988-Science
TL;DR: The elastin receptor complex contains a component of 67 kilodaltons that binds to a glycoconjugate affinity column containing beta-galactoside residues and is eluted from this column with lactose.

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Abstract: The elastin receptor complex contains a component of 67 kilodaltons that binds to a glycoconjugate affinity column containing beta-galactoside residues and is eluted from this column with lactose. This protein component is also released from the surface of cultured chondroblasts by incubation with lactose, and its association with immobilized elastin is inhibited by lactose. Since lactose also blocks elastic fiber formation by cultured chondroblasts, the galactoside-binding property of the elastin receptor is implicated in this process.

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299 citations


Journal ArticleDOI
H R Kaback1, Eugene M. Barnes1Institutions (1)
TL;DR: Preliminary evidence is provided for the concept that the "carriers" of the d-lactic dehydrogenase-coupled transport systems in isolated membrane vesicles from Escherichia coli may be electron transfer intermediates.

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Abstract: The results presented in this paper provide preliminary evidence for the concept that the "carriers" of the d-lactic dehydrogenase-coupled transport systems in isolated membrane vesicles from Escherichia coli may be electron transfer intermediates. Initial rates of lactose transport and d-lactic dehydrogenase activity respond identically to temperature and both processes have the same activation energy of 8400 cal per mole. The steady state levels of lactose accumulation at a variety of temperatures represent equilibrium states in which there is a balance between influx and efflux. This balance can be easily influenced by raising or lowering the temperature. Temperature-induced efflux is a saturable process with an apparent affinity constant that is approximately 60 times higher than the affinity constant for influx determined under the same experimental conditions. The apparent maximum velocity of temperature-induced efflux, on the other hand, is the same as that of influx. Potassium cyanide also induces a saturable efflux phenomenon which has an apparent Km that is much higher than that of the influx process. p-Chloromercuribenzoate inhibits d-lactic dehydrogenase-coupled transport of lactose, galactose, arabinose, glucuronate, glucose-6-P, proline, glutamic acid, serine, alanine, tyrosine, lysine, and tryptophan, and inhibition of each system by p-chloromercuribenzoate is reversed by dithiothreitol. Furthermore, p-chloromercuribenzoate inhibits temperature-induced efflux of intramembranal lactose, exchange of external lactose with [14C]lactose in the intramembranal pool, and lactose efflux induced by 2,4-dinitrophenol. Inhibition of these experimental parameters and of d-lactic dehydrogenase by p-chloromercuribenzoate is reversed by dithiothreitol. Reduction of the respiratory chain between d-lactic dehydrogenase and cytochrome b1 is responsible for carrier-mediated efflux of lactose. Anaerobiosis, cyanide, and 2-heptyl-4-hydroxyquinoline-N-oxide, each of which inhibits electron transfer after cytochrome b1, cause marked efflux. Amytal causes slow efflux, and oxamate and p-chloromercuribenzoate do not cause efflux despite marked inhibition of d-lactic dehydrogenase and the initial rate of lactose transport. Addition of amino acids which are also transported by d-lactic dehydrogenase-coupled transport mechanisms results in little or no inhibition of lactose transport. These findings are discussed in terms of a conceptual working model in which the carriers are depicted as electron transfer intermediates between d-lactic dehydrogenase and cytochrome b1.

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243 citations


Journal ArticleDOI
Ruth G. Doell1, Norman Kretchmer1Institutions (1)
TL;DR: The hypothesis that s-galactosidase in the fetal intestine is induced by circulating lactose is not supported by the evidence presented.

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Abstract: s-Galactosidase has been studied in the intestine of the developing rat and rabbit using both lactose and o -nitrophenyl- s -galactoside as substrates. In the small intestine of rat and human, enzymic activity was maximal in the jejunum, with activity moderate in the duodenum and ileum, minimal in the cecum and absent in the stomach. The intestinal mucosa of the rabbit has been shown to contain two s-galactosidases a particulate enzyme which hydrolyzes both substrates and a soluble enzyme which splits only o -nitrophenyl- s -galactoside. Also, in rat intestine two enzymes are present, but the soluble enzyme has a low pH optimum and approximately equal affinity for both substrates whereas the more active particulate enzyme has a pH optimum near 6 and hydrolyzes lactose much more rapidly than o -nitrophenyl- s -galactoside. The s-galactosidase of human intestine appears to be associated with the particulate fractions of the cell and has considerably more activity towards lactose than o -nitrophenyl- s -galactoside. The hypothesis that s-galactosidase in the fetal intestine is induced by circulating lactose is not supported by the evidence presented.

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238 citations


Journal ArticleDOI
01 Jan 1967-Tetrahedron
Abstract: Selective tribenzoylation of methyl α, d -glucopyranoside, methyl α- d mannopyranoside and methyl α- d -galactopyranoside gives the 2,3,6-tri-O-benzoates in good yield (> 50%); the glucoside gives in addition the 2,4,6-tri-O-benzoate in substantial yield (19% isolated). Selective dibenzoylation of methyl α- d -mannopyranoside and methyl α- d -glucopyranoside gives the 3,6- and 2,6-di-O-benzoates respectively, whereas the corresponding galactopyranoside showed low selectivity. The order of reactivity of the secondary OH groups has been deduced from the results and is different for each glycoside, being 2-OH > 3-OH > 4-OH for the glucoside, 3-OH > 2-OH > 4-OH for the mannoside, and 2-OH, 3-OH > 4-OH for the galactoside. Possible reasons for these differences in reactivity are discussed. PMR spectroscopy is shown to be a useful method for determining the structures of glycoside diesters.

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196 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202110
202011
201913
201815
201710
201611

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Topic's top 5 most impactful authors

Hakon Leffler

11 papers, 166 citations

Norman S. Radin

5 papers, 324 citations

Motoko Nakashizuka

5 papers, 69 citations

P.S. Appukuttan

5 papers, 37 citations

J. Keith Wright

4 papers, 143 citations