N-acetylglucosamine 6-sulfate residues in keratan sulfate and heparan sulfate are desulfated by the same enzyme

We have prepared a series of oligosaccharides to assess the substrate specificity of exo sulfatase activity in cultured human skin fibroblasts toward N-acetylglucosamine-6-sulfate residues present in keratan sulfate (KS) and heparan sulfate (HS). Non-reducing end alpha-GlcNAc-6-SO4 residues (derived from HS) were desulfated by a specific sulfatase that when deficient leads to the accumulation of HS and the expression of mucopolysaccharidosis type IIID (Sanfilippo D). Under the in vitro conditions studied there are two pathways for the degradation of oligosaccharides containing non-reducing end beta-GlcNAc-6-SO4 residues (derived from KS). In one pathway beta-N-acetylglucosaminidase produces GlcNAc-6-SO4 which is then desulfated. In the other pathway the beta-GlcNAc-6-SO4 residue is desulfated and then cleaved by the action of an beta-N-acetylglucosaminidase activity. There was no detectable beta-N-acetylglucosaminidase activity in fibroblasts from a Tay-Sachs patient to produce GlcNAc-6-SO4 from beta-GlcNAc-6-SO4 residues in KS of oligosaccharides. There was approximately 10% of this normal beta-N-acetylglucosaminidase activity in fibroblasts from a Sandhoff patient, suggesting the A and S forms may be involved in this reaction. Desulfation of GlcNAc-6-SO4 residues in KS, HS and the monosaccharide GlcNAc-6-SO4 was considerably reduced or not detected in fibroblasts from a Sanfilippo D patient. As KS was not detected in the urine of a Sanfilippo D patient we propose that KS degradation in these patients proceeds by the action of a beta-N-acetylglucosaminidase activity to produce GlcNAc-6-SO4 which is not further degraded.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnosis of Sanfilippo type A syndrome by estimation of sulfamidase activity using a radiolabelled tetrasaccharide substrate

1. A radiolabelled tetrasaccharide mixture (GlcNS-UA-GlcNS-UOA) containing GlcNSO3-UA-GlcNSO3-L-[6, 3H]idonic acid, GlcNSO3-UA-GlcNSO3-anhydro-L-[6, 3H]idonic acid and GlcNSO3-UA-GlcNSO3-L-[6, 3H]gulonic acid was evaluated together with a radiolabelled disaccharide O-(alpha-2-sulfamino-2-deoxy-D-glucopyranosyl)-(1 leads to 3)-L-[6, 3 H]idonic acid (GlcNS-IdOA) and a trisaccharide GlcNSO3-UA-D-[1, 3 H]glucosaminitol N-sulfate (GlcNS-UA-GlcitolNS) as diagnostic substrates for sulfamidase present in cultured human skin fibroblasts and leucocytes. 2. Sulfamidase activity assessed with GlcNS-UA-GlcNS-UOA was up to 10 times higher than the value obtained for GlcNS-IdOA and the trisaccharide. These results demonstrate that an adjacent GlcNS-UOA disaccharide residue to the sulfaminoglucosamine under attack may play a role in the mechanism of action or binding of sulfamidase toward its substrates. 3. Sulfamidase activity in fibroblast and leucocyte homogenates with GlcNS-UA-GlcNS-UOA exhibited a pH optimum at pH 5.0, an apparent Km of 27 to 50 mumol/l and inhibition by both NaCl and Na2SO4. 4. No detectable sulfamidase activity toward the tetrasaccharide, trisaccharide and disaccharide substrates could be detected using homogenates of fibroblast cultures from Sanfilippo A patients (sulfamidase deficient). Sulfamidase activity assayed with GlcNS-UA-GlcNS-UOA clearly distinguished Sanfilippo A patients from normal controls, heterozygotes and other mucopolysaccharidosis types. Because of the higher activity of sulfamidase toward the tetrasaccharide substrate, compared to that observed for the other substrates evaluated, we recommend its use for the routine enzymic detection of the Sanfilippo A syndrome.

Detection of the Sanfilippo type B syndrome using radiolabelled oligosaccharides as substrates for the estimation of alpha-N-acetylglucosaminidase

1. The following radiolabelled disaccharides were prepared from heparin and evaluated as substrates for alpha-N-acetylglucosaminidase present in cultured skin fibroblasts: O-(alpha-3-acetamido-2-deoxy-D-glucopyranosyl)-(1 leads to 4)-L-[6,3H]idose (GlcNAc-Ido), O-(alpha-2-acetamido-2-deoxy-D-glucopyranosyl)-(1 leads to 4)-1,6 anhydro-L-[6,3H]idose (GlcNAc-anIdo), O-(alpha-2-acetamido-2-deoxy-D-glucopyranosyl)-(1 leads to 4)-L-[6,3H]idose 2-sulfate (GlcNAc-Ido(OS)), O-(alpha 2-acetamido-2-deoxy-D-glucopyranosyl)-(1 leads to 3)-L-[6,3H]idonic acid (GlcNAc-IdOA). 2. Alpha-N-Acetylglucosaminidase activity assessed with GlcNAc-IdOA was 12 times higher than the values obtained using GlcNAc-Ido, GlcNAc-anIdo and GlcNAc-Ido(OS). Less than 5% of normal activity resulted when these substrates were incubated with fibroblasts from Sanfilippo B patients. These results demonstrate that a C6 carboxyl group on the adjacent residue to the N-acetylglucosaminide moiety is an important structural requirement in the mechanism of action or binding of alpha-N-acetylglucosaminidase toward alpha-linked N-acetylglucosaminide residues. The presence of a C2 sulfate group on the adjacent residue had no effect on enzyme activity. 3. Alpha-N-Acetylglucosaminidase activity in leucocyte and fibroblast homogenates assayed using GlcNAc-IdOA as substrate clearly distinguished Sanfilippo B patients from normal controls, and Sanfilippo A, C and D patients.

Enzymatic diagnosis of the mucopolysaccharidoses: experience of 96 cases diagnosed in a five-year period

We assessed lysosomal exohydrolase activities in homogenates of cultured skin fibroblasts and peripheral blood leucocytes of approximately 550 patients referred from throughout Australasia and suspected of having a mucopolysaccharidosis. Of these, 96 patients from 80 families were diagnosed as being homozygous deficient for a particular lysosomal enzyme activity. Clinical phenotype varied considerably within each of the enzyme-deficient states. This did not correlate with the level of "residual" enzyme activity in leucocyte or fibroblast homogenates. It was not always possible to discriminate heterozygotes from normal controls by enzyme assay of leucocyte or fibroblast homogenates in this study of a large number of mucopolysaccharidoses Type II by means of a single hair root assay system.

Implementation, interpretation, and analysis of a suboptimal boundary finding algorithm

This paper presents a suboptimal boundary estimation algorithm for noisy images which is based upon an optimal maximum likelihood problem formulation. Both the maximum likelihood formulation and the resulting algorithm are described in detail, and computational results are given. In addition, the potential power of the likelihood formulation is demonstrated through the presentation of three simple but insightful analyses of algorithm performance. These analyses are based on a technique we have developed for comparing the accuracies of different boundary finding algorithms. This technique also helps in understanding the interplay of object shape and data models in the relative performances of boundary finders. Some of the algorithm design considerations resulting from the use of our analysis technique are new and, at first, surprising. Our technique appears to be the only one developed for comparing the accuracies of different boundary finding algorithms.

Sulphamidase activity in leucocytes, cultured skin fibroblasts and amniotic cells: diagnosis of the Sanfilippo A syndrome with the use of radiolabelled disaccharide substrate

1. Sulphamidase activity was assayed by incubation of the radiolabelled disaccharide O-(alpha-2-sulphamino-2-deoxy-D-glucopyranosyl)- (1 leads to 3)-L-[6-3H]idonic acid with homogenates of leucocytes and cultured skin fibroblasts and concentrates of urine derived from normal individuals, patients affected with sulphamidase deficiency disorder [mucopolysaccharidosis type IIIA (MPS IIIA): the Sanfilippo A syndrome], parents of such patients and patients affected with other mucopolysaccharidoses and lysosomal enzyme deficiencies. 2. The assay clearly distinguished affected homozygotes from normal controls, heterozygotes and other mucopolysaccharidoses types. 3. Sulphamidase displayed remarkable thermal stability; reaction rates were constant for at least 24 h at 60 degrees C for leucocyte and 20 h at 37 degrees C for cultured fibroblast preparations. Apparent Km values for fibroblast sulphamidase were 71 mumol/l at 37 degrees C and 100 mumol/l at 50 degrees C; the corresponding Vmax, values were 21 and 72 pmol min-1 mg-1 of protein respectively. An incubation temperature of 60 degrees C was used for the routine assay of sulphamidase activity in leucocytes, urine and amniotic supernatant preparations. The specific activities of fibroblast and amniotic cell sulphamidase, assessed at incubation temperatures of 37 degrees C, were more than 10-fold the leucocyte enzyme activity at 60 degrees C. 4. We recommend the use of radiolabelled disaccharide substrate for the assay of sulphamidase in leucocytes, skin fibroblasts and urine, for the routine enzymic detection of the sulphamidase deficiency disorder of the Sanfilippo A syndrome.

Screening criteria for the diagnosis of schizophrenia in deaf patients

Confusion about symptoms of schizophrenia in deaf patients leads to misdiagnosis or failure of diagnosis in some individuals. Consequently, we used Schneider's symptoms of schizophrenia, the International Pilot Study of Schizophrenia's list of discriminating symptoms of schizophrenia, and a symptom checklist from DSM-III to evaluate retrospectively 13 deaf adult schizophrenic patients in whom diagnosis were made using DSM-II. Fifteen signs and symptoms were identified in those schizophrenic patients; six symptoms (poor insight, lability of affect, poverty of content, poor rapport, vagueness, and inability to complete a course of action) are usual in nonpsychotic as well as psychotic deaf patients. The nine "primary" symptoms (loss of ego boundaries, delusional perceptions, restricted affect, illogicality, abnormal explanations, hallucinations, inappropriate affect, remoteness from reality, and ambivalence) are useful screening criteria in the diagnosis of schizophrenia in deaf patients.

Selective depolymerisation of heparin to produce radio-labelled substrates for sulfamidase, 2-acetamido-2-deoxy-alpha-D-glucosidase, acetyl-CoA:2-amino-2-deoxy-alpha-D-glucoside N-acetyltransferase, and 2-acetamido-2-deoxy-D-glucose 6-sulfate sulfatase

Heparin was carboxyl-reduced with NaBT4, and degraded under conditions of acid hydrolysis that selectively cleaved the 2-0-sulfo-L-idopyranosidic linkages. The resulting, radiolabelled-disaccharides and -tetrasaccharides were isolated by gel chromatography, and then fractionated by ion-exchange chromatography, paper chromatography, and paper electrophoresis. Of the nine disaccharides isolated and identified, eight were probably derived from the major repeating-disaccharide unit in heparin (2-deoxy-2-sulfoamino-D-glucosyl 6-sulfate leads to L-idosyluronic acid 2-sulfate). Sodium borotritide reduction and/or HNO2 deamination of these eight disaccharide fractions indicated four to contain L-idopyranose residues and the other four to contain 1,6-anhydro-L-idopyranose residues as terminal units. The latter, terminal unit probably represents a minor component formed during the acid hydrolysis. On the basis of N-acetylation, N-sulfation, and HNO2-deamination studies, and the known positions and configurations of the glycosidic and sulfate linkages in heparin, four disaccharides were identified as 0-(2-amino-2-deoxy-alpha-D-glucopyranosyl)-(1 leads to 4)-L-[6-3H]idopyranose, 0-(2-amino-2-deoxy-alpha-D-glycopyranosyl)-(1 leads to 4)-L-[6-3H]idopyranose 2-sulfate, and 0-(2-amino-2-deoxy-alpha-D-glucopyranosyl 6-sulfate]-(1 leads to 4)-L-[6-3H]idopyranose 2-sulfate. A similar set of four disaccharides contained 1,6-anhydro-L-[6-3H]idopyranose residues in place of the L-[6-3H]idopyranose residues. The other disaccharide was tentatively identified as 0-(2-acetamido-2-deoxy-alpha-D-glucopyranosyl)-(1 leads to 4)-L-[6-3H]idopyranose, the isolation of which suggests the presence of an IdA(OSO-3)-GlcNAc-IdA(OSO-3) sequence in the heparin preparation, which accounts for at least 1% of its total sequence. The tetrasaccharides were fractionated, on the basis of their sulfate content, into at least five species by ion-exchange chromatography or by paper electrophoresis. These were fractionated further into species with and without carboxyl groups, and with L-idopyranose or 1,6-anhydro-L-idopyranose residues as terminal units. Tentative structures for some of these tetrasaccharides are proposed. Disaccharide and tetrasaccharide species were evaluated before and after N-acetylation or N-sulfation, as substrates for sulfamidase, acetyl-CoA: 2-amino-2-deoxy-alpha-D-glucoside N-acetyl-transferase, 2-acetamido-2-deoxy-alpha-D-glucosidase, or 2-acetamido-2-deoxy-D-glucose 6-sulfate sulfatase in human-skin fibroblasts.

Radiolabelled oligosaccharides as substrates for the estimation of sulfamidase and the detection of the Sanfilippo type A syndrome

(1) A series of tritiated oligosaccharides, 2-sulfamino-2-deoxy-D-[1-14C]glucose (GlcNS) and [sulfamino-34S]heparin were evaluated as substrates for sulfamidase present in cultured human skin fibroblasts. (2) The following radiolabelled disaccharides were prepared from heparin: O-(alpha-2-sulfamino-2-deoxy-D-glucopyranosyl)-(1 leads to 3)-L-[6,3H]idonic acid (GlcNS-IdOA) and O-(alpha-2-sulfamino-2-deoxy-D-glucopyranosyl)-(1 leads to 3)-2,5 anhydro-L-[6,3H]idonic acid (HlcNS-anIdOA). Other radiolabelled oligosaccharides evaluated as sulfamidase substrates were the disaccharides O-(alpha-2-sulfamino-2-deoxy-D-glucopyranosyl)-(1 leads to 4)-L-[6,3H]idose (GlcNS-Ido) and O-(alpha-2-sulfamino-2-deoxy-D-glucopyranosyl)-)1 leads to 4)-L-[6,3H]idose 2-sulfate (GlcNS-Ido(OS)) and a preparation containing the tetrasaccharide GlcNS-UA-GlcNS-l-idonic acid, GlcNS-UA-GlcNS-anhydro-L-idonic acid and GlcNS-UA-GlcNS-L-gulonic acid. (3) Sulfamidase activity assessed with GlcNS-IdOA and GlcNS-anIdOA were approximately equal and up to 4, 8 and 800 times higher than the value obtained using [sulfamino-35S]heparin, GlcNS-Ido(OS) and GlcNS-Ido respectively. Under the assay conditions used GlcNS was not de-N-sulfated. These results demonstrate that C6 carboxyl and C2 sulfate ester groups on the adjacent residue to the sulfaminoglucosamine moiety are important structural requirements in the mechanism of action or binding of sulfamidase toward N-sulfated disaccharides. The results obtained for a partially characterized mixture of tetrasaccharides suggest that they are degraded four times faster than their disaccharide structural counterparts. (4) No detectable sulfamidase activity toward [sulfamino-35S]heparin, monosaccharide, disaccharide or tetrasaccharide substrates could be detected using homogenates of fibroblast cultures from Sanfilippo A patients (sulfamidase deficient). (5)sulfamidase activity measured with GlcNS-IdOA exhibited a pH optimum at 4.5 to 5.5, an apparent Km of approximately 220 mumol/l and potent inhibition by sulfate ions.

The diagnosis of the Sanfilippo C syndrome, using monosaccharide and oligosaccharide substrates to assay acetyl-CoA: 2-amino-2-deoxy-alpha-glucoside N-acetyltransferase activity

Glucosamine, galactosamine, mannosamine, several disaccharides and a tetrasaccharide were evaluated as substrates for the N-acetyltransferase involved in the pathogenesis of the Sanfilippo C syndrome. Glucosamine and alpha-D-glucosaminide disaccharides and a tetrasaccharide derived from heparin were exo-N-acetylated by homogenates of cultured skin fibroblast from normal individuals at pH 6.0 in the presence of acetyl-CoA, whereas fibroblast homogenates prepared from a Sanfilippo C patient failed to catalyse the N-acetyltransferase from acetyl-CoA to these substrates. The apparent Km values of the glucosamine and alpha-glucosaminide disaccharide N-acetyltransferase were 98 and 200 mumol/l respectively; the corresponding V values were 200 and 180 nmol.min-1.g-1 fibroblast whole cell homogenate protein respectively. Incubation of homogenates from normal individuals or the Sanfilippo C patient with glucosamine 6-phosphate and acetyl-CoA at pH 6.0 produced N-acetylglucosamine 6-phosphate. Acetyltransfer to glucosamine or glucosamine 6-phosphate in homogenates of normal fibroblasts was not inhibited by the addition of arylamines. It is proposed that N-acetyltransferase to glucosamine, glucosamine 6-phosphate and arylamines is carried out by separate enzymes. Glucosamine is a suitable substrate for the diagnostic assay of the enzyme involved in the exo-N-acetylation of alpha-glucosaminide residues at the non-reducing end of the heparan sulfate stored and excreted by Sanfilippo C patients.

A fatal case of salmonellosis in a dugong

Salmonella lohbruegge was isolated from the kidney and the liver of a captive dugong calf (Dugong dugon) which died after an illness of at least several weeks. Clinical signs included diarrhoea and anorexia and were apparent for a week before death. Necropsy and histopathologic examination revealed thickening of the intestinal mucosa, epithelial degeneration, and epithelioid cell infiltration of mucosa, submucosa and contiguous smooth muscle. Enlargement of intestinal lymphoid tissue was apparent, and occasional focal granulomas were found in the liver. The source of the Salmonella infection was not ascertained.

De novo purine synthesis in avian liver. Co-purification of the enzymes and properties of the pathway

The enzymes of the de novo purine biosynthetic pathway have been partially co-purified from pigeon liver by a method dependent upon the use of the nonionic polymer polyethylene glycol for enzyme stabilization and cofractionation. Although the enzymes did not appear to constitute a large macromolecular complex it was evident that some particular inter-relationship between them was preserved during the purification procedure. Analysis of the end products and pathway intermediates was carried out primarily by sensitive high pressure liquid chromatographic techniques. Substrate and cofactor requirements were confirmed and optimal conditions of pH, temperature, and K+ ion activation established. At phosphoribosyl pyrophosphate (PP-ribose-P) concentrations below 0.3 mM the activity of the first pathway enzyme amidophosphoribosyltransferase was rate-limiting, and the inhibition of this enzyme by AMP regulated the rate of purine ring synthesis. At higher concentrations of PP-ribose-P, aminoimidazole ribonucleotide synthetase, the fifth enzyme of the pathway became rate limiting and was subject to inhibition by added AMP. It was evident that the regulation of purine synthesis was quite complex and that AMP inhibition (perhaps reflected in a low adenylate energy charge) can be effected at different points on the purine pathway.