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PubMed1985

Human alpha-L-iduronidase. 2. Catalytic properties.

The kinetic parameters of human liver alpha-L-iduronidase were determined with three disaccharide substrates: alpha-L-iduronosyl(1----4)2,5-anhydro-D-[1-3H]mannitol 6-sulphate, alpha-L-iduronosyl(1----4)2,5-anhydro-D-[1-3H]mannitol and alpha-L-iduronosyl(1----3)2,5-anhydro-D-[1-3H]talitol 4-sulphate, derived from the natural substrates heparin and dermatan sulphate and one synthetic, fluorogenic substrate, 4-methylumbelliferyl alpha-L-iduronide. The enzyme activity with all four substrates was optimal at about pH 4.5. The Km values derived using the disaccharide substrates were elevated up to 10-fold with up to a 6.5-fold increase in ionic strength whereas that for the synthetic substrate was only increased by 1.7-fold. The V values for all substrates were unaffected. The inhibitory effect of NaCl, Na2SO4, NaH2PO4 or CuCl2 on enzyme activity was more pronounced with the disaccharide substrates than with the synthetic substrate. The moiety which is most important in binding is the idopyranosyl residue. While the aglycone residue adds to the net affinity for the enzyme, it is the substituent groups of both residues which appear to control catalysis. Specifically the carboxyl moiety of the alpha-L-iduronic acid residue is essential for catalysis while the presence of sulphate on the C4 or C6 position of the aglycone residue has a major influence on catalysis rather than binding. alpha-L-Idosyl(1----4)2,5-anhydro-D-[1-3H]mannitol 6-sulphate did not undergo catalysis and was a potent inhibitor of enzyme activity, whereas beta-glucuronosyl(1----4)2,5-anhydro-D-[1-3H]mannitol 6-sulphate, alpha-L-iduronosyl-2-sulphate(1----4)2,5-anhydro-D-[1-3H]-mannitol 6-sulphate and 4-methylumbelliferyl alpha-L-idoside did not undergo catalysis and were not inhibitory. A model of the catalytic requirements of alpha-L-iduronidase is proposed.

Catalysis↗
PubMed1989

Purification, characterization and subcellular localization of pig liver alpha-L-iduronidase.

alpha-L-Iduronidase was purified about 100,000-fold from pig liver by employing column chromatography on cellulose phosphate (P11), concanavalin A-Sepharose 4B, heparin-Sepharose 4B, Toyopearl HW-55, Sephadex G-100 and chelating Sepharose 6B charged with cupric ions. The molecular mass of the purified enzyme was estimated to be 70 kDa by Sephadex G-100 column chromatography. The purified enzyme gave a single band on disc polyacrylamide gel electrophoresis without using sodium dodecyl sulfate. However, two separate components of 70 kDa and 62 kDa appeared when it was analyzed by SDS/polyacrylamide gel electrophoresis. These 70-kDa and 62-kDa components were confirmed as alpha-L-iduronidase immunochemically. The isoelectric points of these enzymes were both 9.1 as measured by isoelectric focusing in a polyacrylamide gel containing ampholine and sucrose. The optimal pH and Km values were 3.0-3.5 and 65 microM 4-methylumbelliferyl-alpha-L-iduronide, respectively. The purified enzyme was stable in the pH range 3.5-6.0 under conditions with or without 0.5 M NaCl. However, in the presence of 0.5 M NaCl, it was unstable at pH 3.0. Moreover, it was conversely stabilized at pH 7.0 in the presence of 0.5 M NaCl. Immunohistochemically, the enzyme was found in the Kupffer cells and was abundant on their lysosomal membranes. In liver cells, however, the immunohistochemical reaction was weak.

Animals↗
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↗
PubMed1984

Human alpha-L-iduronidase. I. Purification and properties of the high uptake (higher molecular weight) and the low uptake (processed) forms.

Two major forms of human alpha-L-iduronidase have been individually purified over 175,000-fold to apparent homogeneity by sequential anion exchange, lectin affinity, and gel filtration chromatography. The two forms, initially designated as soluble and membrane-associated, were extracted from human lung in approximately equal amounts. Optimal solubilization of the membrane-associated form was facilitated by use of a non-ionic detergent or mannose 6-phosphate and saponin. Following detergent homogenization, the two forms were separated by anion exchange chromatography and then individually purified. The more electronegative form was membrane-associated, had a pI of approximately 5.9, and was selectively taken up (high uptake) by cultured Hurler syndrome fibroblasts; the more electropositive soluble form had a pI of about 6.6 and was incorporated into Hurler fibroblasts at a markedly lower rate (low uptake). After treatment with alkaline phosphatase, the pI values of both enzymes were about 7.8. Using 4-methylumbelliferyl-alpha-L-iduronide as substrate, the low and high uptake forms were each purified in milligram quantities to specific activities of 284,000 and 202,000 units/mg, respectively, with a combined yield greater than 35%. Each purified enzyme form migrated as a single protein band which also stained for enzymatic activity when electrophoresed in 7% native polyacrylamide disc gels at pH 4.3. By gel filtration, the high uptake form had an Mr = 85,000 whereas the Mr for the low uptake form was 68,000. Molecular weight estimates by analytical polyacrylamide gel electrophoresis were 82,000 and 70,000 for the high and low uptake forms, respectively. Rabbit anti-human low uptake alpha-L-iduronidase antibodies cross-reacted with the high uptake form as demonstrated by both immunotitration and Ouchterlony double immunodiffusion. Amino acid analysis revealed that the high uptake (higher molecular weight) form contained more arginine, glycine, alanine, glutamate or glutamine, leucine, isoleucine, histidine, and proline residues per molecule than the low uptake (lower molecular weight) form. Automated Edman degradation determined that the NH2-terminal residues of both forms were blocked. Both sodium dodecyl sulfate-polyacrylamide gel electrophoresis and high performance liquid chromatography demonstrated that each purified form was composed of several components; each post-high performance liquid chromatographic component retained catalytic activity and was immunologically cross-reactive with antibodies against the low uptake form.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1980

Studies on the alpha-L-iduronidase activity of beta-glucuronidase preparations from bovine liver, rat liver, and rat preputial gland.

A commercial preparation of bovine liver beta-glucuronidase contained two distinct enzyme species, both of which catalyze the hydrolysis of 4-methylumbelliferyl alpha-L-iduronide. The species with a molecular weight of about 290,000 was devoid of phenyl alpha-L-iduronidase activity and exhibited 4-methylumbelliferyl beta-D-glucuronidase activity. The species with a molecular weight of about 78,000 was active towards phenyl alpha-L-iduronide but lacked the latter activity. Studies of the kinetics of inhibition and heat inactivation suggested that the hydrolysis of 4-methylumbelliferyl alpha-L-iduronide is due to the beta-glucuronidase in the case of the 290,000-dalton species. The highly purified beta-glucuronidase preparations derived from rat preputial gland and liver lysosomes also exhibited 4-methylumbelliferyl alpha-L-iduronidase activity. These findings support the view that beta-glucuronidase can hydrolyze certain alpha-L-iduronide bonds and raise the possibility that beta-glucuronidase may play a role in the catabolism of iduronic acid-containing glycosaminoglycans.

Animals↗
PubMed1996

Molecular genetic defect underlying alpha-L-iduronidase pseudodeficiency.

Mucopolysaccharidosis type I (i.e., Hurler, Hurler-Scheie, and Scheie syndromes) and type II (i.e., Hunter syndrome) are lysosomal storage disorders resulting from alpha-L-iduronidase (IDUA) deficiency and iduronate-2-sulfatase (IDS) deficiency, respectively. The a priori probability that both disorders would occur in a single individual is approximately 1 in 5 billion. Nevertheless, such a proband was referred for whom clinical findings (i.e., a male with characteristic facies, dysostosis multiplex, and mental retardation) and biochemical tests indicated these concomitant diagnoses. In repeated studies, leukocyte 4 methylumbelliferyl-alpha-L-iduronidase activities in this kindred were as follows: <1.0 nmol/mg protein/h in the proband and proband's clinically normal sister; 45.3 in mother; and 45.7 in father (normal range 65.0-140). Leukocyte L-O-(alpha-iduronate-2-sulfate)-(1->4)-D-O-2,5-anhydro[1-3H]mannitol-6- sulfate activities were as follows: 0.0 U/mg protein/h in the proband; 5.7 in his sister; 4.9 in mother; and 15.0 in father (normal range 11.0-18.4). Multiple techniques, including automated sequencing of the entire IDS and IDUA coding regions, were employed to unravel the molecular genetic basis of these intriguing observations. The common IDS mutation R468W was identified in the proband, his mother, and his sister, thus explaining their biochemical phenotypes. Additionally, the proband, his sister, and his father were found to be heterozygous for a common IDUA mutation, W402X. Notably, a new IDUA mutation A300T was also identified in the proband, his sister, and his mother, accounting for reduced IDUA activity in these individuals; the asymptomatic sister, whose cells demonstrated normal glycosaminoglycan metabolism, is thus a compound heterozygote for W402X and the new allele. This A300T mutation is the first IDUA pseudodeficiency gene to be elucidated at the molecular level.

Base Sequence↗
PubMedDate not supplied

New phenotype of adult alpha-L-iduronidase deficiency (mucopolysaccharidosis I) masquerading as Friedreich's ataxia with cardiopathy.

Clinical, ultrastructural and biochemical studies are reported in a 42-year-old woman presenting with congenital pes cavus who, at the age of 23 years, developed slowly progressive distal amyotrophies, hypesthesia, bilateral hearing loss and severe cardiopathy leading to death. There were skeletal anomalies, mild reduction of motor NCVs, but no corneal opacity, retinitis pigmentosa, organomegaly or vacuolated lymphocytes. Autopsy disclosed severe thickening of fibrous tissues (endocardium, cerebrospinal dura) with accumulation of vacuolated cells containing glycosaminoglycans in numerous membrane-bound cytoplasmic vacuoles, and/or compound multilamellar or zebra-body-like structures. The CNS, in addition to enlarged perivascular lacunes in cerebral white matter with lipid-containing macrophages, showed neuronal lipid storage in thalamus, hypothalamus, hippocampus, brain stem nuclei, spinal motor neurons and Purkinje cell dendrites. Ultrastructurally, lamellated inclusions containing gangliosides were seen in mesenchymal cells, oligodendrocytes, pericytes and Schwann cells. Neurons contained abundant ceroid but no lamellated inclusions. Neurochemistry revealed decrease of alpha-L-iduronidase activity in brain tissue to 4% of normal, normal activities of other lysosomal enzymes, and normal lipid and ganglioside patterns. While the morphology and neurochemistry data are characteristic of mucopolysaccharidosis I, the phenotype of adult alpha-L-iduronidase deficiency mimicking Friedreich's disease has not been described so far.

Adult↗
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↗
PubMed1985

The clinical spectrum of alpha-L-iduronidase deficiency.

We present five patients with alpha-L-iduronidase deficiency who do not have the typical Hurler or Scheie phenotypes; they are compared to 28 similarly atypical cases from the literature. Phenotypic differences are pointed out and intrafamilial similarities stressed. Among the various possible explanations for this situation, the existence of genetic compounds seems acceptable for some of the cases, but others seem to be caused by different mutations. The elucidation of these alternative possibilities from recent biochemical research is discussed.

Adolescent↗
PubMed2004

Identification and molecular characterization of alpha-L-iduronidase mutations present in mucopolysaccharidosis type I patients undergoing enzyme replacement therapy.

Mucopolysaccharidosis type I (MPS I) is an autosomal recessive lysosomal storage disorder caused by a deficiency of alpha-L-iduronidase (IDUA). Mutations in the gene are responsible for the enzyme deficiency, which leads to the intralysosomal storage of the partially degraded glycosaminoglycans dermatan sulfate and heparan sulfate. Molecular characterization of MPS I patients has resulted in the identification of over 70 distinct mutations in the IDUA gene. The high degree of molecular heterogeneity reflects the wide clinical variability observed in MPS I patients. Six novel mutations, c.1087C>T (p.R363C), c.1804T>A (p.F602I), c.793G>C, c.712T>A (p.L238Q), c.1727+2T>A, and c.1269C>G (p.S423R), in a total of 14 different mutations, and 13 different polymorphic changes, including the novel c.246C>G (p.H82Q), were identified in a cohort of 10 MPS I patients enrolled in a clinical trial of enzyme-replacement therapy. Five novel amino acid substitutions and c.236C>T (p.A79V) were engineered into the wild-type IDUA cDNA and expressed. A p.G265R read-through mutation, arising from the c.793G>C splice mutation, was also expressed. Each mutation reduced IDUA protein and activity levels to varying degrees with the processing of many of the mutant forms also affected by IDUA. The varied properties of the expressed mutant forms of IDUA reflect the broad range of biochemical and clinical phenotypes of the 10 patients in this study. IDUA kinetic data derived from each patient's cultured fibroblasts, in combination with genotype data, was used to predict disease severity. Finally, residual IDUA protein concentration in cultured fibroblasts showed a weak correlation to the degree of immune response to enzyme-replacement therapy in each patient.

Amino Acid Substitution↗
PubMed1992

PCR detection of two RFLPs in exon I of the alpha-L-iduronidase (IDUA) gene.

Two polymorphisms were detected within exon I of the alpha-L-iduronidase (IDUA) gene both of which create restriction endonuclease sites and one of which changes an amino acid. The polymorphisms may be detected by digesting the same 245-bp polymerase chain reaction product. The polymorphisms can be used diagnostically in families with IDUA deficiency (mucopolysaccharidosis type I) and Huntington disease, which is closely linked to the IDUA locus.

Base Sequence↗
PubMed1992

Linkage, but not gene order, of homologous loci, including alpha-L-iduronidase (Idua), is conserved in the Huntington disease region of the mouse and human genomes.

alpha-L-iduronidase (IDUA), which when deficient causes mucopolysaccharidosis type I, is located near the Huntington disease locus (HD) on human Chromosome (Chr) 4p16.3, approximately 10(6) base pairs (bp) from the telomere. As part of our continuing efforts to define a detailed comparative map for this chromosomal segment in mice and humans, we have used an interspecific backcross between C57BL/6J and an inbred strain derived from Mus spretus to map Idua, the mouse homolog of IDUA. We also mapped the mouse homolog of D4S115, an anonymous locus approximately 250 kb proximal to IDUA. As expected, both Idua and D4S115h are located on the proximal portion of mouse Chr 5 near homologs for other loci on human Chr 4p. Comparison of gene order in mice and humans demonstrates, however, that a chromosomal rearrangement within this conserved synteny has occurred since divergence of lineages leading to mice and humans.

Animals↗
PubMed1991

Huntington disease-linked locus D4S111 exposed as the alpha-L-iduronidase gene.

alpha-L-Iduronidase (IDUA) has been intensively studied due to its causative role in mucopolysaccharidosis type I (Hurler, Scheie and Hurler/Scheie syndromes). The recent cloning of a human IDUA cDNA has resulted in a reevaluation of the chromosomal location of this gene. Previously assigned to chromosome 22, IDUA now has been localized to 4p16.3, the region of chromosome 4 associated with Huntington's disease (HD). The existence of a battery of cloned DNA, physical map information, and genetic polymorphism data for this region has allowed the rapid fine mapping of IDUA within the terminal cytogenetic band of 4p. IDUA was found to be coincident with D4S111, an anonymous locus displaying a highly informative multiallele DNA polymorphism. This map location, 1.1 X 10(6) bp from the telomere, makes IDUA the most distal cloned gene assigned to 4p. However, it falls within a segment of 4p16.3 that has been eliminated from the HD candidate region, excluding a role for IDUA in this disorder.

Alleles↗
PubMed1992

Prenatal diagnosis of Hurler disease by analysis of alpha-iduronidase in chorionic villi.

Twenty-four pregnancies at risk for Hurler disease (MPS I) were monitored by measurement of alpha-iduronidase in chorionic villi. Adequate samples were obtained for direct assay of the villi in 22 pregnancies. Five were found to be affected and the pregnancies were terminated. In another pregnancy an equivocal result was obtained on direct assay but analysis of the cultured chorionic cells showed the fetus to be affected. In one pregnancy where an exceptionally small biopsy was obtained, direct assay indicated the fetus to be unaffected. Following amniocentesis this result was shown to be incorrect. These results confirm that, provided an adequate sample is obtained, an accurate diagnosis can be made by direct assay of chorionic villi in pregnancies at risk for Hurler disease.

Amniotic Fluid↗
PubMed2005

Mucopolysaccharidosis I: Alpha-L-Iduronidase mutations in three Tunisian families.

Mucopolysaccharidosis type I (MPS I) is a lysosomal storage disease resulting from the defective activity of the enzyme alpha-L-iduronidase (IDUA). The disease has severe and milder phenotypic subtypes. The IDUA mutations in five MPS I patients from three unrelated families from central and southern Tunisia were determined by amplifying and sequencing each of the IDUA exons and intron-exon junctions. Two novel IDUA mutations, c.1805delTinsGAACA in exon 13 and I270S in exon 7, and two previously reported mutations, P533R and R628X, were detected. The two patients in family 1 who had the Hurler phenotype were homoallelic for the novel deletion-insertion mutation. The patient in family 2 who also had the Hurler phenotype was heteroallelic for the novel missense mutation I270S and the previously reported nonsense mutation R628X. The two patients in family 3 who had the Hurler-Scheie phenotype were homoallelic for P533R. In addition, six known IDUA polymorphisms were identified. These are the first Tunisian MPS I patients to be genotyped. The identification of these mutations and their genotype-phenotype correlations should facilitate prenatal diagnosis and counselling for MPS I in Tunisia, where a very high rate of consanguinity exists.

Alleles↗
PubMed2007

Ectopic expression of a conifer Abscisic Acid Insensitive3 transcription factor induces high-level synthesis of recombinant human alpha-L-iduronidase in transgenic tobacco leaves.

We are examining various plant-based systems to produce enzymes for the treatment of human lysosomal storage disorders. Constitutive expression of the gene encoding the human lysosomal enzyme, alpha-L-iduronidase (IDUA; EC 3.2.1.76) in leaves of transgenic tobacco plants resulted in low-enzyme activity, and the protein appeared to be subject to proteolysis. Toward enhancing production of this recombinant enzyme in vegetative tissues, transgenic tobacco plants were generated to co-express a CaMV35S:Chamaecyparis nootkatensis Abscisic Acid Insensitive3 (CnABI3) gene construct, along with the human gene construct. The latter contained regulatory sequences of the Phaseolus vulgaris arcelin 5-I gene (5'-flanking, signal-peptide-encoding, and 3'-flanking regions). Ectopic synthesis of the CnABI3 protein led to the transactivation of the arcelin promoter and accordingly high activity (e.g., 25,000 pmol/min/mg total soluble protein) and levels of recombinant IDUA mRNA and protein were induced in leaves of transgenic tobacco, particularly in the presence of 150-200 microM S-(+)-ABA. Synthesis of human IDUA containing a carboxy-terminal ER retention (SEKDEL) sequence was also inducible by ABA in leaves co-transformed with the CnABI3 gene. As compared to the natural S-(+)-ABA, two persistent ABA analogues, (+)-8' acetylene ABA and (+)-8'methylene ABA, led to greater levels of beta-glucuronidase (GUS) reporter activities in leaves co-expressing the CnABI3 gene and a vicilin:GUS chimeric gene. In contrast, (+)-8' acetylene ABA and natural ABA appeared to be equally effective in stimulating the CnABI3-induced expression of an arcelin:GUS gene, and of the human IDUA gene, the latter also driven by arcelin-gene-regulatory sequences. Various stress-related treatments, particularly high concentrations of NaCl, had an even greater effect than ABA in promoting accumulation of human IDUA in co-transformed tobacco leaves. This strategy provides the means of enhancing the yields of recombinant proteins in transgenic plant vegetative tissues and potentially in cultured plant cells. The human recombinant protein can be readily induced in the presence of chemicals such as NaCl that can be added to cell cultures or even whole plants without a significant increase in production costs.

Abscisic Acid↗