Biomedical subjects

R DeGasperi

Publications and source records attributed to R DeGasperi.

25 records · Page 2Linked to original sources

PubMed1988

A GM2-specific beta-hexosaminidase from the roe of striped mullet (Mugil cephalus).

The roe of striped mullet (Mugil cephalus) was found to contain a beta-hexosaminidase different from the beta-hexosaminidases isolated from other sources. The enzyme from mullet roe is able to cleave GalNAc from GM2 without the assistance of either an activator protein or a detergent. It also cleaves the oligosaccharide derived from GM2 and other oligosaccharides containing the GM2 sequence GalNAc beta 4(NeuAc alpha 3)Gal-. However, it is not effective in hydrolyzing neutral glycosphingolipids containing terminal GalNAc or GlcNAc, such as GbOse4Cer, GgOse3Cer, or LcOse3Cer. These results indicate that mullet roe beta-hexosaminidase can specifically cleave GalNAc from the glycoconjugates containing the GM2 sequence. No beta-hexosaminidase with such specificity has been previously described. Thus, this unique enzyme should be very useful for the detection and analysis of glycoconjugates containing the oligosaccharide chains with GM2 sequence.

Animals↗

PubMed1987

Isolation and characterization of gangliosides with hybrid neolacto-ganglio-type sugar chains.

We have previously reported the presence of GM2 as the major ganglioside in the roe of striped mullet, Mugil cephalus, (Li, Y.-T., Hirabayashi, Y., DeGasperi, R., Yu, R. K., Ariga, T., Koerner, T. A. W., and Li, S.-C. (1984) J. Biol. Chem. 259, 8980-8985). In addition to GM2, mullet roe also contain a series of gangliosides with thin-layer chromatographic mobilities slower than GM2. Besides enzymatic hydrolysis and NMR spectroscopy, we have employed the thin-layer chromatography overlay technique using a human monoclonal IgM antibody which recognizes the GM2 epitope to study the nature of these gangliosides. Using these methods we have isolated and characterized three novel mullet roe gangliosides with the following structures: (Formula: see text). These three gangliosides all contain neolacto-series sugar chains. However, the unique feature of gangliosides 5 and 10 is that the terminal portion of the sugar chain is of the ganglio-series while the internal portion is of the neolacto series structure. Due to the substitution of a GalNAc on the internal Gal in 9 and 10 in the inner core, these two gangliosides also contain the gangliotriaosyl structure. Thus, the sugar chains in these gangliosides are of novel type and can be considered a hybrid between the two series which can be defined as the neolacto-ganglio series.

Animals↗

PubMed1986

A unique glycosphingolipid-splitting enzyme (ceramide-glycanase from leech) cleaves the linkage between the oligosaccharide and the ceramide.

A novel type of enzyme which hydrolyzes the linkage between the ceramide and the sugar chain in various glycosphingolipids has been found in the leech, Hirudo medicinalis. This enzyme releases the intact oligosaccharide from LacCer, GbOse3Cer, GbOse4Cer, GbOse5Cer, nLcOse4Cer, GM3, GM2, GM1, GD1a and GT1 with the concurrent release of ceramides. By using tritium-labeled GM1 as substrate we found the optimum pH of this enzyme to be between pH 4 and 5. Since the enzyme cleaves the linkage between the ceramide and the sugar chain in various glycosphingolipids with no apparent preference toward the sugar chain, we propose to call this enzyme ceramide-glycanase.

Animals↗

PubMed1986

Urinary endo-beta-galactosidase capable of depolymerizing polylactosaminoglycans.

Human urine was found to contain an endo-beta-galactosidase capable of depolymerizing sulfated and non-sulfated polylactosaminoglycans. Using 0.05 M sodium phosphate buffer, pH 7.0, this enzyme was not retained by DEAE-Sephadex A-50 or concanavalin A-Sepharose. The urinary endo-beta-galactosidase liberated a disaccharide with chromatographic mobility identical to 6-O-sulfo-GlcNAc beta 1----3Gal as one of the major products from keratan sulfates isolated from whale nasal cartilage, bovine cornea, and human costal cartilage. It also liberated GlcNAc beta 1----3 Gal as one of the major oligosaccharides from erythroglycan. The oligosaccharide profiles produced from various keratan sulfates and erythroglycan by the action of urinary endo-beta-galactosidase are quite similar to those produced by Escherichia freundii endo-beta-galactosidase (Nakagawa, H., Yamada, T., Chien, J.-L., Gardas, A., Kitamikado, M., Li, S.-C., and Li, Y.-T. (1980) J. Biol. Chem. 255, 5955-5959). The presence of urinary endo-beta-galactosidase indicates the existence of a new catabolic pathway for polylactosaminoglycans. This pathway involves the cleavage of internal beta-galactosyl linkages of the glycan chain.

Galactosidases↗

PubMed1984

Isolation and characterization of a novel phytosphingosine-containing GM2 ganglioside from mullet roe (Mugil cephalus).

The major ganglioside from the roe of striped mullet (Mugil cephalus) has been isolated and purified. Compositional analysis of this ganglioside revealed that it contained an equimolar ratio of the following residues: N-acetylneuraminic acid, N-acetylgalactosamine, galactose, glucose, and the long-chain base. Further structural studies by sequential enzymatic hydrolysis, permethylation analysis, and proton NMR spectroscopy indicated that the structure of the oligosaccharide moiety was identical to that of GM2 ganglioside from human brain: GalNAc beta 1----4Gal beta 1----4(3----2 alpha NeuAc)-Glc----ceramide. This ganglioside, however, differed from brain GM2 in its ceramide portion. The most striking differences are the presence of large amounts of C18 and C20 phytosphingosine (over 80% of the total long-chain bases) and the preponderance of monounsaturated alpha-hydroxy fatty acids (over 80%). Such a phytosphingosine-containing GM2 ganglioside has never been reported.

Animals↗

PubMed1984

Characterization of human liver 3-O-beta-D-glucopyranuronosyl-cholesterol by mass spectrometry and nuclear magnetic resonance spectroscopy.

We have isolated an unusual acidic glycolipid which was detected in the lower phase of the Folch partition of the total lipid extract of human liver during a routine isolation of glycosphingolipids. With the solvent systems commonly used for thin-layer chromatography of glycosphingolipids, this glycolipid has a mobility similar to GbOse3Cer, one of the major glycosphingolipids in human liver. Free cholesterol was released from this glycolipid upon treatment with beta-glucuronidase. The electron impact mass spectrum of the permethylated derivative of this glycolipid showed an intense peak at m/e 369 which is consistent with the cholesterol part of the molecule. It also showed m/e 233 and 201 which are derived from the permethylated glucopyranuronosyl residue. The final proof of the structure was accomplished by high resolution NMR spectroscopy which revealed the presence of beta-linked glucopyranuronosyl residue and cholesterol. Thus, the structure of this acidic glycolipid was conclusively established to be 3-O-beta-D-glucopyranuronosyl-cholesterol.

Cholesterol↗

PubMed1983

Presence of activator proteins for the enzymic hydrolysis of GM1 and GM2 gangliosides in normal human urine.

Normal human urine has been found to contain activator proteins that stimulate the enzymic hydrolysis of GM1 and GM2 gangliosides. These two activators were partially purified by Sephadex G-200 filtration and DEAE-Sephadex A-50 chromatography. The presence of these two activators was assayed by demonstrating the stimulation of the in vitro hydrolysis of GM1 and GM2 gangliosides. As little as 50 ml of urine is sufficient to detect the presence of these two activators. The crude activator preparation from normal urine was also found to stimulate the hydrolysis of galactosylceramide sulfate by arylsulfatase A.

Adult↗