An improved method for the isolation and assay of the acid lipase from human liver.

An improved method for the isolation and assay of the lysosomal acid lipase from human liver has been developed. Over 90% of the enzymatic activity was extracted in soluble form by brief homogenization of frozen tissue with the nonionic surfactant, Triton X-100. With cholesterol, [1-14C]oleate and 4-methylumbelliferyl plamitate as substrate in emulsions with the amphoteric surfactant, N-tetradecyl-N,N,-dimethyl-3-ammonio-1-propanesulfonate, and ethanol, an apparent V of 1.9 nmol . min-1 . mg-1 protein was obtained with the radioactive substrate and 29 nmol . min-1 . mg-1 protein with the fluorogenic substrate analog, respectively. The released radioactivity-labelled oleic acid was quantitated by selective extraction with a new biphasic solvent system containing carbon tetrachloride and hexane. This assay procedure offers the advantages over other procedures that subcellular fractionation of the tissue is not required for the isolation of the cellular fractionation of the tissue is not required for the isolation of the enzyme; the enzymatic activity toward these emulsions is much greater than previously reported for other methods of substrate solubilization and cholesterol esters with saturated and unsaturated fatty acids can be employed as substrate since both types of fatty acids can be efficiently partitioned and quantitated with this solvent system.

Characterization of unusual hexosaminidase A (HEX A) deficient human mutants.

Two families with unusual hexosaminidase A (HEX A) mutations are described. In one, the proband had the Tay-Sachs disease phenotype with considerable HEX A activity. In the second, the proband was phenotypically normal with absent HEX A activity. Activities using ganglioside GM2 as substrate demonstrate markedly reduced activities in the first case and half-normal activities in the second. Pedigree analyses indicate the presence of two different mutations. In the first, the proband appears to be an allelic compound HEX A 2-4 where mutation HEX A 4 leads to a diminution of HEX A activity against GM2 but not for the synthetic substrate, 4MU-beta-D-N-acetyl-glucosaminide, with HEX A 2 being the Tay-Sachs disease (or similar) mutation. In the second family, the proband is an allelic compound HEX A 2-5 where mutation HEX A 5 leads to a diminution of HEX A activity against the synthetic substrate, 4MU-beta-D-N-acetyl-glucosaminide, but not for GM2. The presence of either mutation will lead to false-negative (HEX A 4) or false-positive (HEX A 5) assignments of heterozygosity or homozygosity for GM2 gangliosidosis when synthetic substrates are employed. In both families, DM2 N-acetyl-beta-D-galactosaminidase activity in fibroblasts was an accurate determinant of phenotype.

Clinical and biochemical expression of a unique mucopolysaccharidosis.

A boy who presented with painful joints leading to contractures was found to have a mucopolysaccharidosis not previously described. He had severe dysostosis multiplex of the long bones but nearly normal intellectual development and no involvement of the cornea. Lysosomal storage vacuoles were noted in dermal endothelial cells; these were similar to those seen in the genetic mucopolysaccharidoses. Mucopolysacchariduria was not excessive in amount but it was distinctly abnormal in pattern and his excretion of dermatan sulfate resembled that found in the Hunter and Hurler syndromes. The activities of the lysosomal hydrolases in cultured fibroblasts were normal or increased. The degradation of accumulated 35S-mucopolysaccharide in fibroblasts in culture was typical of a mucopolysaccharidosis. His mother accumulated 35S-mucopolysaccharides in fibroblasts, suggesting an X-linked inheritance of the disorder.

Lysosomal storage disorders. Diagnosis by ultrastructural examination of skin biopsy specimens.

Fifteen patients with lysosomal storage diseases were studied. Diagnoses of their illnesses included infantile Gaucher disease; Krabbe disease; Niemann-Pick disease, type A; glycogen storage disease, type 3; Fabry disease, Jansky-Bielschowsky and Spielmeyer-Vogt types of amaurotic idiocy, GM1 gangliosidosis, type 1; Hurler disease; and Sanfilippo disease, types A and B. We carried out ultrastructural examinations of skin biopsy specimens that were taken to establish a cultured fibroblast line on each patient. We found diagnostic storage inclusions in all patients except those with infantile Gaucher disease, Krabbe disease, and Spielmeyer-Vogt disease, This technique can be carried out on a specimen obtained by a primary physician on an out-patient basis, thus avoiding major surgery.

Sanfilippo disease type B: enzyme replacement and metabolic correction in cultured fibroblasts.

alpha-Acetylglucosaminidase, purified from human placent, corrected the defect in mucopolysaccharide degradation when added to culture fibroblasts from patients with Sanfilippo disease type B. A small cellular concentration of enzyme gave a large corrective effect. The half-life of disappearance of enzyme activity was 4 to 7 days.

Tay-Sachs disease: prenatal diagnosis.

Fifteen pregnant women with a 25 percent risk of delivering a child with Tay-Sachs disease were monitored by amniocentesis and hexosaminidase A assays of amniotic fluid, uncultured amniotic cells, and cultured amniotic cells. Tay-Sachs disease was diagnosed prenatally in six fetuses; the diagnosis was confirmed in one child after birth and in five fetuses after therapeutic abortion. Prenatal diagnosis indicated the absence of Tay-Sachs disease in nine other fetuses; this diagnosis was confirmed postnatally in six, three are still in utero.