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At least 19 recordsLinked to original sources
PubMed1976

alpha-L-iduronidase activity in leukocytes: diagnosis of homozygotes and heterozygotes of the Hurler syndrome.

The activity of alpha-L-iduronidase was determined in leukocytes from two patients with the Hurler syndrome, five obligatory heterozygotes, one patient with the Hunter syndrome, and ten normal individuals. It was found that the determination of alpha-L-iduronidase in leukocytes was a useful method for differential diagnosis between the Hurler and Hunter syndromes. Heterozygotes of the Hurler syndrome showed approximately 50% level of alpha-L-iduronidase activity in leukocytes as compared with that of normal individuals. This suggests that the determination of alpha-L-iduronidase activity may be available for the carrier detection of the Hurler syndrome.

Diagnosis, Differential↗
PubMed1979

A fluorometric assay using 4-methylumbelliferyl alpha-L-iduronide for the estimation of alpha-L-iduronidase activity and the detection of Hurler and Scheie syndromes.

Incubation of 4-methylumbelliferyl alpha-L-iduronide with whole cell homogenates prepared from cultured skin fibroblasts and amniotic cells, and peripheral blood leukocytes gave 4-methylumbelliferone which was easily measured fluorometrically. This reaction, presumably due to the action of alpha-L-iduronidase, has a maximum hydrolytic activity at pH 3.25. The apparent KM value of alpha-L-iduronidase in leukocyte whole cell homogenates for this substrate was 179 mumol/l compared to 353, 41 and 166 mumol/l for other alpha-L-iduronidase substrates phenyl alpha-L-iduronide, iduronosyl anhydrol[1-3H]mannitol 6-sulfate and iduronosyl anhydro[1-3H]mannitol respectively; the corresponding Vmax values were 617, 394, 158 and 10 pmol/min/mg protein respectively. Incubation of the 4-methylumbelliferyl alpha-L-iduronide with whole cell homogenates prepared from cultured skin fibroblasts and leukocytes from a Hurler patient gave 4-methylumbelliferone at a rate more than 20 times less than found for control normal preparations. 4-Methylumbelliferyl alpha-L-iduronide is a sensitive, convenient and superior substrate to phenyl alpha-L-iduronide for the assay of alpha-L-iduronidase activity, but is not a suitable replacement for the radiolabelled substrate iduronosyl anhydro[1-3H]mannitol 6-sulfate.

Amniotic Fluid↗
PubMed1979

alpha-L-iduronidase, beta-D-glucuronidase, and 2-sulfo-L-iduronate 2-sulfatase: preparation and characterization of radioactive substrates from heparin.

Radioactive disaccharide substrates for alpha-L-iduronidase, beta-D-glucuronidase, and 2-sulfo-L-iduronate 2-sulfatase have been prepared from heparin by deaminative cleavage followed by reduction with NaBT4. Six disaccharides were isolated from this reaction mixture and identified. Acid hydrolysis of the major disaccharide, O-(alpha-L-idopyranosyluronic acid 2-sulfate)-(1 linked to 4)-(2,5-anhydro-D-mannitol-l-t 6-sulfate (IdAs--Ms), produced 48% of O-(alpha-L-idopyranosyluronic acid)-(1 linked to 4)-(2,5-anhydro-D-mannitol-l-t 6-sulfate) (IdA--Ms) and 25% of O-(alpha-L-idopyranosyluronic acid)-(1 linked to 4)-2,5-anhydro-D-mannitol-l-t. The most-sensitive substrate for determining alpha-L-iduronidase activity was IdA--Ms which, when incubated with leucocyte and skin-fibroblast homogenates prepared from patients having a deficiency of alpha-L-iduronidase (Mucopolysaccharidosis Type I; MPS-I), was hydrolysed to yield 2,5-anhydro-D-mannitol-l-t 6-sulfate at a rate 50-times less than that found for normal control-preparations. Similarly, O-(beta-D-glucopyranosyluronic acid)-(1 linked to 4)-(2,5-anhydro-D-mannitol-l-t 6-sulfate) was degraded by whole-cell homogenates prepared from beta-D-glucuronidase-deficient (Mucopolysaccharidosis, Type VII) fibroblasts, to yield 2,5-anhydro-D-mannitol-l-t 5-sulfate at a rate 60-times less that that found for MPS-I and normal control-preparations. IdAs--Ms was degraded by 2-sulfo-L-iduronate 2-sulfatase at a rate more than 45-times greater than that found for O-(alpha-L-idopyranosyluronic acid 2-sulfate)-(1 linked to 4)-2,5-anhydro-D-mannitol-l-t. C-6 Sulfation of the anhydro-D-mannitol-l-t residue is an important structural determinant in the mechanism of action of both alpha-L-iduronidase and 2-sulfo-L-iduronate 2-sulfatase on disaccharide substrates.

Cells, Cultured↗
PubMed1979

Direct demonstration of binding of a lysosomal enzyme, alpha-L-iduronidase, to receptors on cultured fibroblasts.

Receptor-binding of "high-uptake" forms of lysosomal enzymes to human diploid skin fibroblasts had been predicted from the Michaelis--Menten kinetics of uptake of these enzymes [e.g., Sando, G.N. & Neufeld, E.F. (1977) Cell 12, 619--627]. We have now demonstrated such binding directly by using a sensitive assay for the bound enzyme. Cells deficient in alpha-L-iduronidase were detached from plastic dishes by mild trypsinization, allowed to recover, and used in suspension. They were incubated with urinary alpha-L-iduronidase at 0 degrees C for 90 minutes and then washed by centrifugation through concentrated bovine serum albumin; the activity of the cell-associated enzyme was measured with 4-methylumbelliferyl alpha-L-iduronide as substrate. A Scatchard analysis showed 14,000 binding sites per cell and a Kd of 1 x 10(-9) M for high-uptake alpha-L-iduronidase; binding of the low-uptake form was barely detectable. Mannose 6-phosphate, a known competitive inhibitor of uptake, inhibited the binding competitively, with Ki = 1 x 10(-4) M. Unexpectedly, mannose 6-phosphate greatly accelerated the dissociation of bound enzyme. During uptake of alpha-L-iduronidase at 35 degrees C, the receptors were regenerated every few minutes, even in the absence of protein synthesis.

Calcium↗
PubMed1978

Substrates for the assay of alpha-L-iduronidase.

Procedures are described for the preparation of two disaccharides, 4-O-alpha-L-iduronosyl-2,5-anhydro[3H]mannitol and 3-O-alpha-L-iduronosyl-2,5-anhydro[3H]-talitol, from heparin and dermatan sulfate, respectively. These disaccharides lend themselves to an easy assay of alpha-L-iduronidase which is based on the fractionation of the liberated neutral anhydro[3H]mannitol or anhydro[3H]talitol from the unreacted substrate by adsorption of the latter to Dowex 1. Investigation of the reaction conditions showed that the alpha-L-iduronidase activity (enzyme from human fibroblasts and Helix pomatia) was optimal at pH 3.6 in acetate buffer containing 0.01 M NaCl with iduronosyl-2,5-anhydro[3H]mannitol as substrate. For iduronosyl-2,5-anhydro[3H]talitol the pH optimum was 4.0 with the H. pomatia enzyme. The KM for iduronosyl-2,5-anhydro[3H]mannitol was 0.23 mM with human fibroblasts and 0.04 mM with Helix enzyme; a KM value of 0.02 mM was determined for iduronosyl-2,5-anhydro[3H]talitol with the Helix alpha-L-iduronidase.

Cells, Cultured↗
PubMed1977

Variant of iduronidase deficient mucopolysaccharidoses: further evidence for genetic heterogeneity.

An alpha-L-iduronidase deficiency syndrome has been described in adult male twins, which was phenotypically distinct from that of the Hurler and Scheie syndromes or the chondroitinsulphaturias. Multiple dysostosis and stiff joints were present without cloudy corneae, cardiac involvement and mental or physical retardation. This clinical phenotype appeared to be a newly recognized allelic mutation at the iduronidase locus but does not exclude a non-allelic mutation coding for a subunit of the iduronidase molecule.

Adolescent↗
PubMed1976

Hurler syndrome: alpha-L-iduronidase activity in leukocytes as a method for heterozygote detection.

Alpha-L-Iduronidase activity and beta-galactosidase activity were determined in mixed leukocyte preparations in 10 families in which the Hurler syndrome had occurred. Affected patients, heterozygotes, and normal subjects were clearly distinguished by alpha-L-iduronidase activity alone. Patients had 0-3%, obligate heterozygotes 19-60%, and normal subjects 83-121% of the mean normal activity. There was no overlap between heterozygotes and normal subjects. Although the mean alpha-L-iduronidase to beta-galactosidase ratio was significantly lowered in heterozygotes when compared with that of normal subjects, appreciable overlap was noted between the two groups.

Adolescent↗
PubMed1977

A radioactive substrate and assay for alpha-L-iduronidase.

A novel radioactive substrate for alpha-L-iduronidase, anhydro[3H]mannitol-iduronide has been prepared. This compound is hydrolysed by alpha-L-iduronidase to yield anhydro[3H]mannitol, which can be separated from the substrate and counted. The assay, described for use with fibroblast homogenates, is satisfactory for the diagnosis of mucopolysaccharidosis I.

Clinical Enzyme Tests↗
PubMed1978

Fluorometric measurement of urinary alpha-L-iduronidase activity.

A fluorogenic substrate for alpha-L-iduronidase, 4-methylumbelliferyl alpha-L-iduronide, has been newly synthesized and the enzyme activity has been measured in urine samples obtained from normal persons and patients suffering from mucopolysaccharidosis. Urine samples derived from a patient with Scheie syndrome showed greatly reduced activity compared with a normal adult at a similar age. This patient exhibited a high level of urinary excretion of dermatan sulfate and heparan sulfate, which could be interpreted in terms of her low alpha-L-iduronidase activity. The use of the fluorogenic substrate has some advantages over existing methods because of the high sensitivity and the relative ease of handling, and it should be useful not only for diagnosis but also for following the purification process of the enzyme.

Adult↗
PubMed1976

alpha-L-iduronidase deficiency and possible Hurler-Scheie genetic compound. Clinical, pathologic, and biochemical findings.

The enzymatic delineation of the mucopolysaccharidoses has revealed that certain syndromes, although phenotypically distinct, share the same enzymatic defect. Patients with the classic Hurler and Scheie syndromes or other phenotypic variations of these two disorders have a deficiency of alpha-L-iduronidase. We are reporting a patient with alpha-L-iduronidase deficiency whose phenotypic abnormalities did not resemble either the Hurler or Scheie syndrome and who may have had either the Hurler-Scheie genetic compound described by McKusick or an allelic disorder. Our patient was a 25-year-old woman whose initial presentation was due to acute paranoia and who was subsequently found to have many morphologic, neurologic, radiographic, and neuropathologic findings consistent with a mucopolysaccharide disorder. To our knowledge, complete neuropathologic findings have not been previously described in this hybrid group of patients. A distinctive feature of this patient's illness is that the underlying disorder was not clinically apparent until adulthood, but presented with sever bony abnormalities of the skull and deposition of mucopolysaccharides in the meninges.

Adult↗
PubMed1976

Atypical Hurler syndrome without alpha-L-iduronidase deficiency.

Three atypical patients with clinical and laboratory findings of Hurler syndrome, but without alpha-L-iduronidase deficiency, are described. Clinical features included characteristic facies, mental retardation, corneal clouding, dysostosis multiplex, restriction of joint mobility, and hepatosplenomegaly. Excessive amounts of chondroitin sulfate B and heparitin sulfate were excreted in the urine. alpha-L-Iduronidase activities in leucocytes and liver tissues were within the normal range or somewhat elevated.

Adolescent↗
PubMed1977

alpha-L-Iduronidase activity in established lymphoblastoid cells from patients with Hurler and Scheie syndromes transformed by Epstein-Barr virus.

alpha-L-Iduronidase activity was determined in established lymphoblastoid cells, which were transformed in vitro by Epstein-Barr virus, of lymphocytes-rich cell populations isolated from peripheral blood of patients with Hurler and Scheie syndromes. alpha-L-Iduronidase activities in established lymphoblastoid cells from patients were undetectable, while activities of control subjects were clearly detected. These results suggest that established lymphoblastoid cells are useful for the enzymatic study of genetic mucopolysaccharidoses.

Adolescent↗
PubMed1976

The iduronidase-deficient mucopolysaccharidoses: clinical and roentgenorgraphic features.

Hurler and Scheie syndromes, two of the six clinically distinct mucopolysaccharidoses, are deficient in the same lysosomal enzyme, alpha-L-iduronidase. A third group of iduronidase-deficient patients can now be identified during the pediatric years using clinical and radiographic criteria. Based on inferential evidence for allelism between the Hurler and Scheie genes, the occurrence of genetic compounds which simultaneously carry both mutant alleles may be predicted to occur. This can be considered analogous to the structural gene mutations leading to hemoglobin SC disease. Four patients with phenotypes intermediate between Hurler and Scheie syndromes are flet to represent genetic compounds of this type. Both clinical and roentgenographic features are helpful in distinguishing these patients from those with Hurler syndrome or Scheie syndrome. Fibroblast correction characteristics identical to those of Hurler syndrome and Scheie syndrome and absence of consanguinity are additional features which favor classification as genetic compounds. The possibility of a third mutant allele at the Hurler-Scheie locus or of extreme phenotype variation are not considered likely alternative explantations. Depending on the frequency of the Scheie syndrome and the Hurler syndrome, genetic compounds may occur with an intermediate frequency or may be more common than either homozygous condition.

Adolescent↗
PubMed1976

Detection of the carrier state of Hurler's syndrome by assay of alpha-L-iduronidase in leukocytes.

The mean specific activity of alph-L-iduronidase in leukocytes from six obligate heterozygotes for Hurler's syndrome was found to be slightly less than one-half of the mean in normal controls; no overlap of normal and known heterozygote values was encountered. The assay has been applied with success to six potential heterozygotes, siblings of a child with Hurler's syndrome. Thus heterozygote detection of Hurler's syndrome is clearly possible; this finding, as well as the ready availability of leukocytes for screening tests, recommends their use for examination of potential carrier status in this disorder.

Adult↗
PubMed1976

Leucocyte values of alpha-L-iduronidase activity in mucopolysaccharidosis I.

Assay of alpha-L-iduronidase in peripheral leucocytes is a rapid and simple diagnostic aid in mucopolysaccharidosis I. The mean value for heterozygotes is one-half the value of normal controls, but overlap between the two groups occurs. Use of this assay may be helpful in genetic counselling of selected couples.

Glycoside Hydrolases↗