Human glucosamine-6-sulphatase deficiency. Diagnostic enzymology towards heparin-derived trisaccharide substrates

Purification of a 75 kDa protein from the organelle matrix of human neutrophils and identification as N-acetylglucosamine-6-sulphatase

A 75 kDa protein was purified to homogeneity from granule extracts of normal human granulocytes using Sephadex G-75 chromatography, Mono-S cation exchange chromatography and chromatofocusing. The protein consisted of one chain with a molecular mass of 75 kDa, as determined by SDS/PAGE. Tryptic peptide analysis by MALDI-TOF (matrix-assisted laser-desorption ionization-time-of-flight) MS and sequence analysis by MS/MS identified the protein to be N-acetylglucosamine-6-sulphatase (EC 3.1.6.14). The identity of the protein was confirmed by demostrating enzymatic activity towards the substrate N-acetylglucosamine 6-sulphate. The enzyme was active over a broad pH range with an optimum of pH 7.0, and showed a K(m) value of 13.0 mM and a V(max) value of approximately 1.8 microM/min per mg. The enzyme also showed O-desulphation activity towards heparan sulphate-derived saccharides. Subcellular fractionation of neutrophil organelles showed the presence of enzymatic activity mainly in the same fractions as primary granules. Furthermore, PMA treatment of the neutrophils induced release of the enzyme, indicating its matrix protein nature. The presence of N-acetylglucosamine-6-sulphatase in human neutrophils implies that neutrophils may play a role in the modulation of cell surface molecules and extracellular matrix by O-desulphation.

Biosynthesis of heparan sulphate with diverse structures and functions: two alternatively spliced forms of human heparan sulphate 6-O-sulphotransferase-2 having different expression patterns and properties

Heparan sulphate 6- O -sulphotransferase (HS6ST) catalyses the transfer of sulphate from adenosine 3'-phosphate, 5'-phosphosulphate to the 6th position of the N -sulphoglucosamine residue in HS. We previously described the occurrence of three isoforms of mouse HS6ST, mHS6ST-1, -2, and -3 [Habuchi, Tanaka, Habuchi, Yoshida, Suzuki, Ban and Kimata (2000) J. Biol. Chem. 275, 2859-2868]. In the present study, we have characterized HS6ST-2 and HS6ST-1 human isologues, including their chromosomal localizations. In the process of their cDNA cloning, we found two forms of HS6ST-2: the original (hHS6ST-2) and a short form (hHS6ST-2S) with 40 amino acids deleted. Both hHS6ST-2 and hHS6ST-2S catalysed the same sulphation reaction, but their preferences for sulphation sites in HS substrates were different. Dot-blot analysis of the two forms showed that the original form was exclusively expressed in adult and foetal brain tissues, whereas the short form was expressed preferentially in ovary, placenta and foetal kidney, suggesting that the expression of two forms of hHS6ST-2 is strictly regulated to yield tissue-dependent differences in the fine structure of HS. A refined analysis of their reaction products has led us to another finding, that HS6STs could also transfer sulphate to N -sulphoglucosamine residues located at the non-reducing terminal of HS with high affinity.

Genomic basis of mucopolysaccharidosis type IIID (MIM 252940) revealed by sequencing of GNS encoding N-acetylglucosamine-6-sulfatase

Mucopolysaccharidosis type IIID (MPS IIID; Sanfilippo syndrome type D; MIM 252940) is caused by deficiency of the activity of N-acetylglucosamine-6-sulfatase (GNS), which is normally required for degradation of heparan sulfate. The clinical features of MPS IIID include progressive neurodegeneration, with relatively mild somatic symptoms. Biochemical features include accumulation of heparan sulfate and N-acetylglucosamine-6-sulfate in the brain and viscera. To date, diagnosis required a specific lysosomal enzyme assay for GNS activity. From genomic DNA of a subject with MPS IIID, we amplified and sequenced the promoter and 14 exons of GNS. We found a homozygous nonsense mutation in exon 9 (1063C --> T), which predicted premature termination of translation (R355X). We also identified two common synonymous coding single-nucleotide polymorphisms and genotyped these in samples from four ethnic groups. This first report of a mutation in GNS resulting in MPS IIID indicates the potential utility of molecular diagnosis for this rare condition.

Synthesis and X-ray structures of sulfate esters of fructose and its isopropylidene derivatives. Part 1: 2,3:4,5-di-O-isopropylidene-beta-D-fructopyranose 1-sulfate and 4,5-O-isopropylidene-beta-D-fructopyranose 1-sulfate

2,3:4,5-Di-O-isopropylidene-beta-D-fructopyranose 1-sulfate have been synthesized by treatment of 2,3:4,5-di-O-isopropylidene-beta-D-fructopyranose with pyridine-sulfur trioxide complex. Direct hydrolysis of the isopropylidene group at C-4, C-5 gave 2,3-O-isopropylidene-beta-D-fructopyranose 1-sulfate. The crystal and molecular structures of ammonium (1a) and potassium (1b) salts of diisopropylidene derivative and ammonium (2) salt of monoisopropylidene derivative were determined by X-ray crystallography. Data for 1a and 1b were collected in 120 K and in 150 K for 2. All salts crystallized in P2(1)2(1)2(1) space group. There are three independent anions in asymmetric unit in 1b. Pyranose rings in the diisopropylidene derivative salts studied adopt 2S(0) twist boat conformation, whereas in the monoisopropylidene exists in a slightly distorted chair conformation (4C(1)). A staggered conformation is preferred by the sulfate group as indicated by values of C-(ester)-S-O(terminal) torsion angles: -173.2(4) degrees in 1a, 175.1(6) degrees in anion A of 1b, 170.8(6) degrees in anion C of 1b and 177.9(2) degrees in 2. However, strong interactions such as potassium-oxygen and H-bonds may affect the geometry: in anion B of 1b the value of the torsion angle is 139.4(6) degrees.

A superfamily of metalloenzymes unifies phosphopentomutase and cofactor-independent phosphoglycerate mutase with alkaline phosphatases and sulfatases

Sequence analysis of the probable archaeal phosphoglycerate mutase resulted in the identification of a superfamily of metalloenzymes with similar metal-binding sites and predicted conserved structural fold. This superfamily unites alkaline phosphatase, N-acetylgalactosamine-4-sulfatase, and cerebroside sulfatase, enzymes with known three-dimensional structures, with phosphopentomutase, 2,3-bisphosphoglycerate-independent phosphoglycerate mutase, phosphoglycerol transferase, phosphonate monoesterase, streptomycin-6-phosphate phosphatase, alkaline phosphodiesterase/nucleotide pyrophosphatase PC-1, and several closely related sulfatases. In addition to the metal-binding motifs, all these enzymes contain a set of conserved amino acid residues that are likely to be required for the enzymatic activity. Mutational changes in the vicinity of these residues in several sulfatases cause mucopolysaccharidosis (Hunter, Maroteaux-Lamy, Morquio, and Sanfilippo syndromes) and metachromatic leucodystrophy.

A rapid quantitative assay for the detection of mammalian heparanase activity

Heparan sulphate (HS) is an important component of the extracellular matrix and the vasculature basal laminar which functions as a barrier to the extravasation of metastatic and inflammatory cells. Cleavage of HS by endoglycosidase or heparanase activity produced by invading cells may assist in the disassembly of the extracellular matrix and basal laminar, and thereby facilitate cell migration. Heparanase activity has previously been shown to be related to the metastatic potential of murine and human melanoma cell lines [Nakajima, Irimura and Nicolson (1988) J. Cell. Biochem. 36, 157-167]. To determine heparanase activity, porcine mucosal HS was partially de-N-acetylated and re-N-acetylated with [3H]acetic anhydride to yield a radiolabelled substrate. This procedure prevented the masking of, or possible formation of, new heparanase-sensitive cleavage sites as has been observed with previous methods of radiolabelling. Heparanase activity in a variety of tissues and cell homogenates including human platelets, colonic carcinoma cells, umbilical vein endothelial cells and rat mammary adenocarcinoma cells (both metastatic and non-metastatic variants) and liver homogenates all degraded the substrate in a stepwise fashion from 18.5 to approximately 13, 8 and finally to 4.5 kDa fragments, as assessed by gel-filtration analysis, confirming the substrate as suitable for the detection of heparanase activity present in a variety of cells and tissues. A rapid quantitative assay was developed with the HS substrate using a novel method for separating degradation products from the substrate by taking advantage of the decreased affinity of the heparanase-cleaved products for the HS-binding plasma protein chicken histidine-rich glycoprotein (cHRG). Incubation mixtures were applied to cHRG-Sepharose columns, with unbound material corresponding to heparanase-degradation products. Heparanase activity was determined for a variety of human, rat and murine cell and tissue homogenates. The highly metastatic rat mammary adenocarcinoma and murine lung carcinoma cell lines had four to ten times the heparanase activity of non-metastatic variants, confirming the correlation of heparanase activity with metastatic potential. Human cancer patients had twice the serum heparanase levels of normal healthy adults. The assay will be valuable for the determination of heparanase activity from a variety of tissue and cell sources, as a diagnostic tool for the determination of heparanase potential, and for the development of specific inhibitors of heparanase activity and metastasis.

Sanfilippo type D presenting with acquired language disorder but without features of mucopolysaccharidosis

A 7-year-old girl presented with a language disorder reminiscent of verbal auditory agnosia. Later, she proved to have defective N-acetylglucosamine-6-sulfate sulfatase, the enzyme deficient in Sanfilippo D syndrome. She did not show clinical features of mucopolysaccharidosis. The language disorder had a fluctuating course, which eventually evolved into a progressive dementing encephalopathy.

A fluorimetric enzyme assay for the diagnosis of Sanfilippo disease type D (MPS IIID)

4-Methylumbelliferyl-alpha-N-acetylglucosamine 6-sulphate was synthesized and shown to be a substrate for the lysosomal N-acetylglucosamine-6-sulphate sulphatase (GlcNAc-6S sulphatase). Fibroblasts and leukocytes from 3 different Sanfilippo D patients showed < 1% of mean normal GlcNAc-6S sulphatase activity. The enzymatic liberation of the fluorochrome from 4-methyl-umbelliferyl-alpha-N-acetylglucosamine 6-sulphate requires the sequential action of the GlcNAc-6S sulphatase and alpha-N-acetylglucosaminidase. A normal level of alpha-N-acetylglucosaminidase activity was insufficient to complete the hydrolysis of the reaction intermediate 4-methylumbelliferyl-alpha-N-acetylglucosaminide formed by the GlcNAc-6S sulphatase. A second incubation in the presence of excess alpha-N-acetylglucosaminidase is needed to avoid underestimation of the GlcNAc-6S sulphatase activity.