Human acid beta-glucosidase. Use of inhibitory and activating monoclonal antibodies to investigate the enzyme's catalytic mechanism and saposin A and C binding sites

Fabbro, Diane; Grabowski, Gregory A.

doi:10.1016/s0021-9258(18)98580-7

Cited by 43 publications

(8 citation statements)

References 45 publications

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“…If this applies in vivo, one might expect that each of these activators could compensate for the other. However, Fabbro & Grabowski (1991) have shown that saposin A and SAP-2 have a synergistic effect on fglucocerebrosidase under their assay conditions. This might explain why the two individuals with apparently isolated SAP-2 deficiencies [Christomanou et al (1986[Christomanou et al ( , 1989); Schnabel et al (1991) have shown that one of these patients has a point mutation which only affects the SAP-2 locus] did have clinical features of Gaucher disease (/3-glucocerebrosidase deficiency).…”

Section: Discussionmentioning

confidence: 95%

Additional biochemical findings in a patient and fetal sibling with a genetic defect in the sphingolipid activator protein (SAP) precursor, prosaposin. Evidence for a deficiency in SAP-1 and for a normal lysosomal neuraminidase

Paton¹,

Schmid

Kustermann-Kuhn

et al. 1992

Biochemical Journal

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It has been shown that sphingolipid activator proteins (SAPs) 1 and 2 are encoded on the same gene along with two other putative activator proteins [Fürst, Machleidt & Sandhoff (1988) Biol. Chem. Hoppe-Seyler 369, 317-328 and O'Brien, Kretz, Dewji, Wenger, Esch & Fluharty (1988) Science 241, 1098-1101]. We have undertaken further biochemical investigations on a patient and fetal sibling, who were previously shown to have a unique sphingolipid storage disorder associated with an SAP-2 deficiency [Harzer, Paton, Poulos, Kustermann-Kuhn, Roggendorf, Grisar & Popp (1989) Eur. J. Pediatr. 149, 31-39]. The severity of their disorder suggested that other products of the SAP precursor or prosaposin gene may also be deficient. The turnover of cerebroside sulphate and globotriaosylceramide were investigated and were both impaired in fibroblasts from the patient and fetus. However, the activities of cerebroside sulphate sulphatase and globotriaosylceramide alpha-galactosidase in vitro were normal in cells from the fetus and patient respectively. In addition, there was an increase in cerebroside sulphate concentration in the kidney of the affected fetus. These results indicate that, in addition to the SAP-2 deficiency, there was a defect in SAP-1 function in this disorder. Additional increases in the concentration of monohexosyl- and dihexosyl-ceramide in the fetal kidney probably reflect the deficiency of SAP-2 in the case of monohexosylceramides, and the combined activator deficiency in the case of dihexosylceramides. Lactosylceramide-loading studies confirmed that there was a defect in the turnover of this lipid in fibroblasts from the affected patient and fetus but not from a patient with an isolated SAP-1 deficiency, or from patients with Krabbe disease, GM1 gangliosidosis or galactosialidosis. It has been suggested [Potier, Lamontagne, Michaud & Tranchemontagne (1990) Biochem. Biophys. Res. Commun. 173, 449-456] that the prosaposin gene also codes for lysosomal neuroaminidase. However, we found normal neuraminidase activity in fibroblasts from our patient, using assay conditions which are diagnostic for sialidosis patients. The role of prosaposin gene products in sphingolipid metabolism is discussed in view of our biochemical findings in this genetic disorder.

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Section: Discussionmentioning

confidence: 95%

Additional biochemical findings in a patient and fetal sibling with a genetic defect in the sphingolipid activator protein (SAP) precursor, prosaposin. Evidence for a deficiency in SAP-1 and for a normal lysosomal neuraminidase

Paton¹,

Schmid

Kustermann-Kuhn

et al. 1992

Biochemical Journal

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“…Two mechanisms were proposed to explain the role of saposins in the activation of GSL degradation. (1) Saponins facilitate the interaction between the GSLs and exohydrolases by binding, extracting and presenting the membrane localized lipids to water-soluble enzymes ( Sandhoff and Kolter 1996 ); (2) SAPs bind directly to enzymes, not to GSLs, generating a more active enzymatic complex to hydrolyze GSLs ( Fabbro and Grabowski 1991 ). It was found that deficiency of saposin C led to accumulation of GlcCer within the cells and resulted in a GlcCer storage disease resembling a neurologic form of Gaucher disease (GD; see GlcCer and lysosomal GBA1 in GD s ection), showing the crucial role of this cofactor in the metabolism of this monohexosylceramide ( Kang et al.…”

Section: Chemical Structure Metabolism and Occurrence Of Glucosylceramide And Galactosylceramidementioning

confidence: 99%

Glucosylceramide and galactosylceramide, small glycosphingolipids with significant impact on health and disease

2021

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Numerous clinical observations and exploitation of cellular and animal models indicate that glucosylceramide (GlcCer) and galactosylceramide (GalCer) are involved in many physiological and pathological phenomena. In many cases, the biological importance of these monohexosylcermides has been shown indirectly as the result of studies on enzymes involved in their synthesis and degradation. Under physiological conditions, GalCer plays a key role in the maintenance of proper structure and stability of myelin and differentiation of oligodendrocytes. On the other hand, GlcCer is necessary for the proper functions of epidermis. Such an important lysosomal storage disease as Gaucher disease and a neurodegenerative disorder as Parkinson’s disease are characterized by mutations in the GBA1 gene, decreased activity of lysosomal GBA1 glucosylceramidase and accumulation of GlcCer. In contrast, another lysosomal disease, Krabbe disease, is associated with mutations in the GALC gene, resulting in deficiency or decreased activity of lysosomal galactosylceramidase and accumulation of GalCer and galactosylsphingosine. Little is known about the role of both monohexosylceramides in tumor progression, however, numerous studies indicate that GlcCer and GalCer play important roles in the development of multidrug-resistance by cancer cells. It was shown that GlcCer is able to provoke immune reaction and acts as a self-antigen in Gaucher disease. On the other hand, GalCer was recognized as an important cellular receptor for HIV-1. Together, these two molecules are excellent examples of how slight differences in chemical composition and molecular conformation contribute to profound differences in their physicochemical properties and biological functions.

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“…SAP-C is a 20 kDa protein, obviously in homodimeric structure, and was first isolated from spleen of Gaucher patients (Ho & O'Brien 1971). In contrast to SAP-B, it binds not only to lipids and membranes but also interacts with glucosylceramide-b-glucosidase and stimulates the enzyme directly (Berent & Radin 1981;Fabbro & Grabowski 1991). The b-glucosidase is a water soluble lysosomal enzyme that can associate to membranes.…”

Section: (C) Enzymologymentioning

confidence: 99%

Biosynthesis and degradation of mammalian glycosphingolipids

Sandhoff

Kolter

2003

Phil. Trans. R. Soc. Lond. B

172

121

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Glycolipids are a large and heterogeneous family of sphingolipids that form complex patterns on eukaryotic cell surfaces. This molecular diversity is generated by only a few enzymes and is a paradigm of naturally occurring combinatorial synthesis. We report on the biosynthetic principles leading to this large molecular diversity and focus on sialic acid-containing glycolipids of the ganglio-series. These glycolipids are particularly concentrated in the plasma membrane of neuronal cells. Their de novo synthesis starts with the formation of the membrane anchor, ceramide, at the endoplasmic reticulum (ER) and is continued by glycosyltransferases of the Golgi complex. Recent findings from genetically engineered mice are discussed. The constitutive degradation of glycosphingolipids (GSLs) occurs in the acidic compartments, the endosomes and the lysosomes. Here, water-soluble glycosidases sequentially cleave off the terminal carbohydrate residues from glycolipids. For glycolipid substrates with short oligosaccharide chains, the additional presence of membrane-active sphingolipid activator proteins (SAPs) is required. A considerable part of our current knowledge about glycolipid degradation is derived from a class of human diseases, the sphingolipidoses, which are caused by inherited defects within this pathway. A new post-translational modification is the attachment of glycolipids to proteins of the human skin.

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Human acid beta-glucosidase. Use of inhibitory and activating monoclonal antibodies to investigate the enzyme's catalytic mechanism and saposin A and C binding sites

Cited by 43 publications

References 45 publications

Additional biochemical findings in a patient and fetal sibling with a genetic defect in the sphingolipid activator protein (SAP) precursor, prosaposin. Evidence for a deficiency in SAP-1 and for a normal lysosomal neuraminidase

Additional biochemical findings in a patient and fetal sibling with a genetic defect in the sphingolipid activator protein (SAP) precursor, prosaposin. Evidence for a deficiency in SAP-1 and for a normal lysosomal neuraminidase

Glucosylceramide and galactosylceramide, small glycosphingolipids with significant impact on health and disease

Biosynthesis and degradation of mammalian glycosphingolipids

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