A quantitative mannose 6-phosphate receptor-based in vitro assay for recombinant human N-acetylgalactosamine-4-sulfatase.

An assay was developed, using two similar formats, to simultaneously measure both the lysosomal targeting receptor binding and enzyme activity of the recombinant human enzyme N-acetylgalactosamine-4-sulfatase. This assay also has potential application for all phosphorylated lysosomal enzymes that contain mannose-6-phosphate residues. The receptor was either purified from fetal bovine sera then adsorbed, or produced in situ by growing and fixing diploid human fibroblast-like cells, to a solid phase. The enzyme substrate was 4-methylumbelliferyl sulfate which fluoresces after cleavage of the sulfate moiety. Both the precursor and mature forms of the recombinant enzyme were used to demonstrate the specificity and usefulness of the assay. The assay is rapid and sensitive and has a wide dynamic range. Association between the receptor and the mannose-6-phosphate residues was abrogated in the presence of a competitive inhibitor, mannose 6-phosphate. However, partial activity was still measured when the mature enzyme was incubated in the presence of mannose 6-phosphate when using the fixed fibroblast format. This would indicate that the recombinant enzymes contain at least one terminal sugar moiety other than mannose 6-phosphate which can recognize receptors on the surface of human fibroblast-like cells. Other possible applications of this assay are also discussed.

Improved high-performance liquid chromatographic method for N-acetylgalactosamine-4-sulfate sulfatase (arylsulfatase B) activity determination using uridine diphospho-N-acetylgalactosamine-4-sulfate.

UDP-N-acetylgalactosamine-4-sulfate (UDP-GalNAc-4-S) was isolated from hen oviduct (isthmus) with a yield of 31 mumol per 100 g of wet tissue and used for arylsulfatase B (ASB) activity determination. Two HPLC methods of separation and quantitation of the reaction product were described: (1) an original gradient elution method which makes it possible to determine the reaction product when only partially purified ASB was used and additional uridine derivatives were formed during incubation; (2) an improved, fast isocratic elution method which may be used in the case of purified ASB preparations, devoid of other nucleotide hydrolysing enzymes. For both methods the detection limit was 0.1 nmol of product with standard error of determination < or = 3%. Using the gradient elution method we have found that UDP-GalNAc-4-S was hydrolysed by bovine arylsulfatase B1 most efficiently at pH 5.0 and concentration 0.5 mM with K(m) = 85 microM.

Characterization of the oligosaccharide component of arylsulfatase B from rat liver.

A glycan chain analysis of the total oligosaccharide pool derived from rat liver arylsulfatase B was carried out by. P4 Gel Permeation Chromatography and sequential exoglycosidase digestion. It was found that 71% of rat liver arylsulfatase B oligosaccharides were sialylated. The relative contribution of particular structures in the total glycan pool was as follows: sialylated biantennary complex type glycans with terminal galactose--65%, high-mannose type glycans--15%, biantennary complex type glycans with core fucose and terminal N-acetylglucosamine--5%, O-linked oligosaccharides--3.5%.

Arylsulfatase B is present in crystalloid-containing granules of human eosinophil granulocytes.

Eosinophil granulocytes are characterized by large crystalloid-containing granules whose major contents of highly cationic proteins may play a role in allergic reactions and parasitic infections. Human eosinophils are also rich in arylsulfatase B whose enzymatic activity is localized to a population of small type cytoplasmic granules and used as a marker for such organelles. We utilized immunoelectron microscopy to investigate its subcellular distribution in human eosinophils. The arylsulfatase B antigen was found to be concentrated to both the crystalloid core and the matrix of crystalloid-containing granules as well as in small type granules. Therefore arylsulfatase seems to be present primarily in crystalloid-containing granules in a possibly inactive form (but detected by antibodies) that is converted to an enzymatically active form, e.g. during secretion and formation of small type granules which may derive from the former granules.

Capillary electrophoresis to measure sulfoesterase activity on chondroitin sulfate and heparin derived disaccharides.

Capillary electrophoresis was used to assay sulfoesterase activity on sulfated disaccharides derived from chondroitin sulfate, dermatan sulfate and heparin. The three sulfoesterases studied were chondro-4-O-sulfatase (EC 3.1.6.9) and chondro-6-O-sulfatase (EC 3.1.6.10) from Proteus vulgaris and heparo-2-O-sulfatase from Flavobacterium heparinum. Capillary electrophoresis was used to analyse sulfated disaccharide before and after sulfoesterase treatment and a change in migration time was indicative of the presence of sulfoesterase activity. This assay was used both on purified sulfoesterases and on minor sulfoesterase contaminants present in other enzyme preparations. The high sensitivity of capillary electrophoresis permits the elimination of 35S-radiolabeled substrates normally required to assay sulfoesterases. The high resolution of capillary electrophoresis allows the use of this assay on impure enzyme preparations containing high protein concentrations.

Components and proteolytic processing sites of arylsulfatase B from human placenta.

Previous studies have shown that mature arylsulfatase B purified from human sources is composed of two non-identical chains with apparent molecular masses of 43 kDa and 8 kDa. Arylsulfatase B purified from human placenta in the present study, however, included another 7 kDa component that could be detected only by carbohydrate staining on reducing SDS-PAGE employing the Tris-Tricine system. The 43 kDa and 7 kDa components contained a carbohydrate moiety, but the 8 kDa one did not, as demonstrated by periodic acid-Schiff staining, Con-A lectin blotting, endo-glycosidase treatment and in vitro phosphorylation by UDP-N-acetylglucosamine: lysosomal enzyme N-acetylglucosamine 1-phosphotransferase. The purified arylsulfatase B migrated as a single polypeptide of 58 kDa on non-reducing SDS-PAGE, indicating that the three chains are linked by disulfide bonds. In order to determine the origin of the components, N-terminal sequencing of the isolated polypeptides was performed. As a result, the 43, 7 and 8 kDa components were found to commence with Ala-41, Ala-424 and Asp-466, respectively. These results suggest that after removal of the signal peptide, human arylsulfatase B undergoes proteolytic processing on at least two sites during maturation.

A specific fluorogenic assay for N-acetylgalactosamine-4-sulphatase activity using immunoadsorption.

A method combining immune capture and enzyme detection by fluorochemistry has been developed for the diagnostic assay of N-acetylgalactosamine-4-sulphatase (4-sulphatase). The procedure uses a monoclonal antibody 4-S 4.1 to immunoadsorb 4-sulphatase specifically from complex protein samples containing other sulphatases, and 4-methylumbelliferyl sulphate to detect captured 4-sulphatase. The assay provides an accurate and simple method for the diagnosis of Maroteaux-Lamy syndrome (Mucopolysaccharidosis type VI).

Prenatal diagnosis of mucolipidosis type II on first-trimester amniotic fluid.

We investigated the possibility of prenatal diagnosis of mucolipidosis type II (ML II) by lysosomal enzyme determination on amniotic fluid obtained at 11 weeks of gestation in three pregnancies at risk. Diagnosis of ML II was made in one case on the basis of increased levels of five lysosomal enzymes tested. The diagnosis was confirmed on cultured chorionic cells, their cultured medium, 17-week amniotic fluid, and fetal plasma obtained for confirmation prior to the termination of pregnancy.

Immunoquantification of the low abundance lysosomal enzyme N-acetylgalactosamine 4-sulphatase.

The low abundance lysosomal enzyme N-acetylgalactosamine 4-sulphatase (4-sulphatase) has been quantified using a microimmunopurification step and a monoclonal-based ELISA detection system. The assay is similar in principle to a two-site ELISA but uses a single monoclonal antibody against one epitope to bind 4-sulphatase in two separate assay steps. The sensitivity of this assay is sufficient to allow the quantification of 4-sulphatase in human cultured skin fibroblasts derived from normal controls and patients deficient in 4-sulphatase activity (mucopolysaccharidosis type VI or Maroteaux-Lamy syndrome). The results obtained suggest a range of mucopolysaccharidosis type VI or 4-sulphatase deficient mutants, from those expressing little or no quantifiable 4-sulphatase protein to those examples with quantifiable levels of 4-sulphatase protein which is enzymically inactive. Phenotypic variability in patients with a 4-sulphatase deficiency may therefore be partially attributed to a range of protein expressions. The method should allow the determination of 4-sulphatase specific activity in mucopolysaccharidosis type VI patients.

Arylsulphatases in the rabbit oviduct: postovulatory changes tested by histochemical and biochemical procedures.

A histochemical and biochemical study of the activity of arylsulphatases A and B was carried out on the oviduct of female rabbits during the first days after mating. The histochemical results demonstrated that the ampullary and the isthmic epithelial cells have a positive reaction to the sulphatases during the whole of the postovulatory period tested. The enzymatic activity is mainly localized in the basal cellular cytoplasm. The biochemical results confirmed that both arylsulphatase A and B are active. Arylsulphatase A activity is more intense in the ampulla than in the isthmus and it increases during the whole of the postovulatory period; in the isthmus the activity increases up to 72 h, thereafter decreasing again. The arylsulphatase B activity is always lower than arylsulphatase A activity; maximum activity is reached between 66 to 72 h after mating. The arylsulphatase B is relatively higher in the ampulla than in the isthmus. The biological role of these enzymes is discussed in relation to the regulation of the sulphated glycoconjugates.

A direct-colouring, metal precipitation method for the demonstration of arylsulphatases A and B.

A new, direct-colouring, metal precipitation method for the light microscopical demonstration of arylsulphatases A and B is described. It is based on the reducing capacity of nitrocatechol liberated by arylsulphatases from p-nitrocatechol sulphate. The reaction is carried out in Karnovsky-Roots' copper ferricyanide incubation mixture at pH 5.0 or 5.5; the nitrocatechol liberated reduces ferricyanide to ferrocyanide, which in turn forms a brown precipitate with copper that indicates enzyme activity. Enzyme activity was localized in cytoplasmic particles compatible with a lysosomal localization of the enzyme. The histochemical reaction was inhibited by phosphate, which has been shown to inhibit arylsulphatases A and B in biochemical determinations. The method described is technically simple, and sections can be mounted in synthetic resin after dehydration.

Mucolipidosis II. The clinical, radiological and biochemical features in three cases.

We report on the clinical, radiological and biochemical features of mucolipidosis II in three infants. One with subtle phenotypical findings died at 2 weeks of age without a specific diagnosis. A sibling who died at 2 years of age and another infant, presently 3.5 years of age manifest all the characteristic features of mucolipidosis II: extreme psychomotor delay and failure to thrive, coarse facial features, gingival hyperplasia, joint stiffness, inguinal hernia and skin induration. The corneae were normal and there was no mucopolysacchariduria. Radiologically, these infants show changes which are characteristic but not specific for mucolipidosis II. Cytologically, skin fibroblasts from these patients demonstrate the lysosomal inclusions typical of I-Cell Disease. Biochemically, cultured skin fibroblasts show deficient activity of arylsulphatase A and B and hexosaminidase A and B. These acid hydrolases were increased markedly in plasma and in the culture medium of the skin fibroblasts.

Prenatal diagnosis of metachromatic leukodystrophy: a diagnosis by amniotic fluid and its confirmation.

Late infantile metachromatic leukodystrophy (MLD) was successfully diagnosed in utero by demonstrating the absence of arylsulfatase-A in amniotic fluid using diethylaminoethyl-Sepharose column chromatography. Diagnosis by amniotic fluid using an ion-exchange column is more rapid and reproducible as compared with those reported previously. The diagnosis was confirmed by the absence of arylsulfatase-A in fetal brain, liver, and kidney tissues as well as by the marked accumulation of sulfatide in kidney. The kidney is the most appropriate organ for the demonstration of sulfatide accumulation in fetal tissues in MLD.

Cytochemical localization of arylsulfatase B in rat basophils and mast cells.

Basophils and mast cells possess large metachromatically staining granules which contain sulfated glycosaminoglycans as well as vasoactive compounds. To determine whether these granules might also have lysosomal properties, we used electron microscopy and cytochemistry to localize arylsulfatase B in rat basophils and mast cells. In basophils of bone marrow, enzymatic reaction product was consistently seen in many, but not all, of the basophil granules. In some cells, the enzyme could also be demonstrated in the Golgi region, restricted to a single cisterna and small vesicles. It was never seen in rough endoplasmic reticulum (RER), although the paucity of cells made adequate sampling difficult. In mast cells of bone marrow and the peritoneal cavity, enzymatic reaction product was consistently found in some cytoplasmic granules of varying sizes and shapes where it characteristically rimmed the periphery of the granule just beneath the limiting membrane. It should be emphasized, however, that the majority of granules were not reactive. Reaction product could also be found occasionally in segments of RER, and in the Golgi region with a distribution similar to that of the basophil. The presence of lysosomal arylsulfatase in granules of developing basophils in bone marrow suggests that some basophil granules, like those of neutrophils, eosinophils, and monocytes are primary lysosomes. Some mast cell granules also contain this lysosomal enzyme, although it is not clear from the present data whether these granules are primary or secondary lysosomes.