g(m1)-ganglioside and Leukodystrophy--Globoid-Cell

Topics: alpha-Galactosidase; Arylsulfatases; beta-Galactosidase; Cystine; Fabry Disease; G(M1) Ganglioside; G(M2) Ganglioside; Galactosylceramidase; Gangliosidoses; Genetic Carrier Screening; Glycoproteins; Heparitin Sulfate; Humans; Hydrolases; Isoelectric Focusing; Isoenzymes; Kinetics; Leukodystrophy, Globoid Cell; Leukodystrophy, Metachromatic; Lipid Metabolism, Inborn Errors; Lysosomes; Metabolism, Inborn Errors; Molecular Weight; Mucolipidoses; Niemann-Pick Diseases; Sphingolipidoses; Sphingomyelin Phosphodiesterase

Topics: Adolescent; Adult; Animals; beta-Galactosidase; Cats; Cerebrovascular Disorders; Child, Preschool; Coronary Disease; Fabry Disease; Female; G(M1) Ganglioside; G(M2) Ganglioside; Gangliosidoses; Gaucher Disease; Glycolipids; Hexosaminidases; Humans; Infant; Infant, Newborn; Leukodystrophy, Globoid Cell; Leukodystrophy, Metachromatic; Male; Sodium-Potassium-Exchanging ATPase; Vascular Resistance

The metabolism of galactosylceramide and lactosylceramide in cultured fibroblasts was studied using the lipid-loading test. These compounds were incorporated into the fibroblasts yet only small amounts of the incorporated lipids were hydrolyzed unless additional phospholipid was mixed with the glycolipid before loading. Among phospholipids, phosphatidylserine was the most effective for incorporation and hydrolysis of the glycolipids, while phosphatidylcholine inhibited the incorporation of the glycolipids. Using filtration techniques, light scattering analyses and subcellular fractionation, the particle size of glycolipid in the culture medium was found to be critically important for the incorporation of the lipids into the cells and their transportation to the lysosomes. The particle sizes of the glycolipids were decreased by mixing with phosphatidylserine. Furthermore, the negative charge in phosphatidylserine may be necessary for the glycolipid transportation into the lysosomes. In fibroblasts from patients with globoid cell leukodystrophy, 40-50% of galactosylceramide was hydrolyzed on the 4th day of culture, a time when the control fibroblasts had hydrolyzed it about 80%. This finding is in contrast with observations made on fibroblasts with other sphingolipidoses which showed near-zero degradation in corresponding substrate-loading tests. In fibroblasts from patients with either globoid cell leukodystrophy of GM1-gangliosidosis, hydrolysis of lactosylceramide was fairly normal yet somewhat lower than control values on any day of culture, thereby indicating that, in the loading tests, lactosylceramide seems to be hydrolyzed with similar levels of enzyme activities by two distinct beta-galactosidases, galactosylceramidase and GM1-ganglioside beta-galactosidase.

Topics: beta-Galactosidase; Cell Line; Cell Membrane; Cerebrosides; Fibroblasts; G(M1) Ganglioside; Galactosylceramides; Gangliosidoses; Glycosphingolipids; Humans; Hydrolysis; Lactosylceramides; Leukodystrophy, Globoid Cell; Lysosomes; Particle Size; Phosphatidylserines

Two genetically distinct acid beta-galactosidases are apparently involved in the hydrolysis of galactosylceramide in fibroblasts. These beta-galactosidases were activated by different bile salts. The classical galactosylceramidase (galactosylceramidase I, EC 3.2.1.46) was activated by sodium taurocholate, while the other galactosylceramidase (galactosylceramidase II) was activated by sodium cholate. The former was genetically lacking in globoid cell leukodystrophy (GLD) and the latter in GM1 gangliosidosis. Galactosylceramidase II cross-reacted with antibody raised against purified GM1 ganglioside beta-galactosidase (EC 3.2.1.23) from the human placenta. The purified beta-galactosidase had galactosylceramidase II activity, which was competitively inhibited by GM1 ganglioside. Thus, galactosylceramidase II seems to be identical to GM1 ganglioside beta-galactosidase and lactosylceramidase II. Galactosylceramidase II had a very low affinity for galactosylsphingosine. In the galactosylceramide-loading tests using fibroblasts from patients with GLD and GM1 gangliosidosis, both cell lines hydrolyzed the incorporated galactosylceramide, with lower rates than control fibroblasts but higher than the fibroblasts from patients with I-cell disease, in which both galactosylceramidase I and II were deficient. These results indicate that galactosylceramide is hydrolyzed by two genetically distinct beta-galactosidases and explain well that galactosylsphingosine but not galactosylceramide accumulates in the brain of patients with GLD.

Topics: beta-Galactosidase; Cell Line; Cerebrosides; Chemical Precipitation; Cholic Acid; Cholic Acids; Cross Reactions; Enzyme Activation; Female; Fibroblasts; G(M1) Ganglioside; Galactosidases; Galactosylceramidase; Galactosylceramides; Gangliosidoses; Humans; Hydrogen-Ion Concentration; Immunologic Techniques; Leukodystrophy, Globoid Cell; Placenta; Pregnancy; Psychosine; Substrate Specificity; Taurocholic Acid

A new fluorogenic compound--6-hexadecanoylamino-4-methyl-umbelliferyl-beta-D-gala cto pyranoside (HMGal), a substrate for human galactocerebroside beta-D-galactosidase (HG), has been synthesized. A method for determining the HG activity based on the use of HMGal as a fluorogenic substrate has been developed. The specificity of HMGal hydrolysis by HG has been demonstrated in experiments with enzyme preparations from human skin fibroblasts and leukocytes in normally and in hereditary glycolipidosis (GM1-gangliosidosis and Krabbe's disease). The use of HMGal permits to markedly increase the sensitivity of the method used for determining the HG activity.

Topics: Chemical Phenomena; Chemistry; Chromogenic Compounds; Clinical Enzyme Tests; G(M1) Ganglioside; Galactosidases; Galactosylceramidase; Gangliosidoses; Humans; Leukodystrophy, Globoid Cell

An assay procedure was developed for accurate estimation of lactosylceramidase II in the presence of relatively high activity of lactosylceramidase I. The procedure involves determination of lactosylceramide-cleaving activities under two different assay conditions, and lactosylceramidase II activity is calculated by the difference. Applicability of the procedure was evaluated with separated soluble fractions of the two beta-galactosidases from normal human brains, and with whole homogenates of gray and white matter, liver and cultured fibroblasts from control individuals and from patients with globoid cell leukodystrophy or GM1-gangliosidosis. The use of the lactosylceramidase I assay procedure developed by Wenger, D.A., Sattler, M., Clark, C. and McKelvey, H. ((1974) Clin. Chim. Acta 56, 199-206) and of the present procedure permits accurate diagnosis of both globoid cell leukodystrophy and GM1-gangliosidosis with one natural substrate, lactosylceramide, irrespective of the relative proportion of the two beta-galactosidases in the tissue.

Topics: beta-Galactosidase; Brain; Ceramides; Clinical Enzyme Tests; Fibroblasts; G(M1) Ganglioside; Galactosidases; Galactosylceramidase; Gangliosidoses; Humans; Isoenzymes; Kinetics; Lactose; Leukodystrophy, Globoid Cell; Liver

Topics: Animals; Brain; Ceramides; Dogs; Enzyme Activation; G(M1) Ganglioside; Galactosidases; Galactosylceramidase; Genotype; Heterozygote; Isoenzymes; Lactose; Leukodystrophy, Globoid Cell; Liver; Organ Specificity; Taurocholic Acid