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Hydrolysis of GM1-ganglioside by human liver beta-galactosidase isoenzymes.

ABSTRACT: 1. GM(1)-ganglioside, specifically tritiated in the terminal galactose, was hydrolysed by two forms of ;acid' methylumbelliferyl beta-galactosidase isolated on gel filtration. 2. Identification of GM(1)-ganglioside beta-galactosidase activity with the ;acid' methyl-umbelliferyl beta-galactosidases was based on the following: coincident elution profiles on gel filtration; simultaneous inactivation by heat and other treatments; stabilization of both activities by chloride ions; mutual inhibition of hydrolysis by the two substrates. 3. The two isoenzymes (I) and (II) showed general requirements for a mixture of anionic and nonionic detergents in the hydrolysis of the natural substrate. 4. Isoenzyme (I) differed from (II) in molecular size, pH-activity profile, relative resistance to dilution and in sensitivity to various inhibitors. 5. The most significant difference between the isoenzymes is in substrate saturation kinetics: (I) was hyperbolic whereas (II) was sigmoid. The apparent Michaelis constants were 28mum for (I) and 77mum for (II). Isoenzyme (I) was insensitive to GM(2)-ganglioside whereas (II) was inhibited, consistent with the hypothesis that GM(1)-ganglioside (and its analogue) acts as modifier in isoenzyme (II) but not in (I). 6. Isoenzyme (I) was membrane-bound whereas (II) was soluble; the former probably represents isoenzyme (II) bound to membrane components, thereby becoming activated. 7. Membranes may serve a dual role in enzyme catalysis involving lipids: as a medium where both enzyme and substrate are effectively concentrated, and as actual activator of enzymes through binding of the latter to specific membrane components.

SUBMITTER: Ho MW

PROVIDER: S-EPMC1165961 | biostudies-other | 1973 Oct

REPOSITORIES: biostudies-other

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SialidaseNeu3action on GM1 ganglioside is neuroprotective in GM1 Gangliosidosis

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2023-12-14 | GSE241844 | GEO

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Incorporation and metabolism of exogenous GM1 ganglioside in rat liver.

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Synthesis of a New β-Galactosidase Inhibitor Displaying Pharmacological Chaperone Properties for GM1 Gangliosidosis.

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GM1 Ganglioside Inhibits ?-Amyloid Oligomerization Induced by Sphingomyelin.

Project description:?-Amyloid (A?) oligomers are neurotoxic and implicated in Alzheimer's disease. Neuronal plasma membranes may mediate formation of A? oligomers in vivo. Membrane components sphingomyelin and GM1 have been shown to promote aggregation of A?; however, these studies were performed under extreme, non-physiological conditions. We demonstrate that physiological levels of GM1 , organized in nanodomains do not seed oligomerization of A?40 monomers. We show that sphingomyelin triggers oligomerization of A?40 and that GM1 is counteractive thus preventing oligomerization. We propose a molecular explanation that is supported by all-atom molecular dynamics simulations. The preventive role of GM1 in the oligomerization of A?40 suggests that decreasing levels of GM1 in the brain, for example, due to aging, could reduce protection against A? oligomerization and contribute to the onset of Alzheimer's disease.

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Carbohydrate mimicry between human ganglioside GM1 and Campylobacter jejuni lipooligosaccharide causes Guillain-Barre syndrome.

Project description:Molecular mimicry between microbial and self-components is postulated as the mechanism that accounts for the antigen and tissue specificity of immune responses in postinfectious autoimmune diseases. Little direct evidence exists, and research in this area has focused principally on T cell-mediated, antipeptide responses, rather than on humoral responses to carbohydrate structures. Guillain-Barré syndrome, the most frequent cause of acute neuromuscular paralysis, occurs 1-2 wk after various infections, in particular, Campylobacter jejuni enteritis. Carbohydrate mimicry [Galbeta1-3GalNAcbeta1-4(NeuAcalpha2-3)Galbeta1-] between the bacterial lipooligosaccharide and human GM1 ganglioside is seen as having relevance to the pathogenesis of Guillain-Barré syndrome, and conclusive evidence is reported here. On sensitization with C. jejuni lipooligosaccharide, rabbits developed anti-GM1 IgG antibody and flaccid limb weakness. Paralyzed rabbits had pathological changes in their peripheral nerves identical with those present in Guillain-Barré syndrome. Immunization of mice with the lipooligosaccharide generated a mAb that reacted with GM1 and bound to human peripheral nerves. The mAb and anti-GM1 IgG from patients with Guillain-Barré syndrome did not induce paralysis but blocked muscle action potentials in a muscle-spinal cord coculture, indicating that anti-GM1 antibody can cause muscle weakness. These findings show that carbohydrate mimicry is an important cause of autoimmune neuropathy.

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SialidaseNeu3action on GM1 ganglioside is neuroprotective in GM1 Gangliosidosis

Project description:SialidaseNeu3action on GM1 ganglioside is neuroprotective in GM1 Gangliosidosis

| PRJNA1010227 | ENA

Crystallographic structure of human beta-hexosaminidase A: interpretation of Tay-Sachs mutations and loss of GM2 ganglioside hydrolysis.

Project description:Lysosomal beta-hexosaminidase A (Hex A) is essential for the degradation of GM2 gangliosides in the central and peripheral nervous system. Accumulation of GM2 leads to severely debilitating neurodegeneration associated with Tay-Sachs disease (TSD), Sandoff disease (SD) and AB variant. Here, we present the X-ray crystallographic structure of Hex A to 2.8 A resolution and the structure of Hex A in complex with NAG-thiazoline, (NGT) to 3.25 A resolution. NGT, a mechanism-based inhibitor, has been shown to act as a chemical chaperone that, to some extent, prevents misfolding of a Hex A mutant associated with adult onset Tay Sachs disease and, as a result, increases the residual activity of Hex A to a level above the critical threshold for disease. The crystal structure of Hex A reveals an alphabeta heterodimer, with each subunit having a functional active site. Only the alpha-subunit active site can hydrolyze GM2 gangliosides due to a flexible loop structure that is removed post-translationally from beta, and to the presence of alphaAsn423 and alphaArg424. The loop structure is involved in binding the GM2 activator protein, while alphaArg424 is critical for binding the carboxylate group of the N-acetyl-neuraminic acid residue of GM2. The beta-subunit lacks these key residues and has betaAsp452 and betaLeu453 in their place; the beta-subunit therefore cleaves only neutral substrates efficiently. Mutations in the alpha-subunit, associated with TSD, and those in the beta-subunit, associated with SD are discussed. The effect of NGT binding in the active site of a mutant Hex A and its effect on protein function is discussed.

| S-EPMC2910082 | biostudies-literature

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