Rodent and human acid -glucosidase. Purification, properties and inhibition by antibodies. Investigation in type II glycogenosis

A Personal History of Cystinosis by Dr. Jerry Schneider

Cystinosis is a rare lysosomal storage disease that is tightly linked with the name of the American physician and scientist Dr. Jerry Schneider. Dr. Schneider (1937–2021) received his medical degree from Northwestern University, followed by a pediatrics residency at Johns Hopkins University and a fellowship in inherited disorders of metabolism. He started to work on cystinosis in J. Seegmiller’s laboratory at the National Institutes of Health (NIH) and subsequently moved to the UC San Diego School of Medicine, where he devoted his entire career to people suffering from this devastating lysosomal storage disorder. In 1967, Dr. Schneider’s seminal Science paper ‘Increased cystine in leukocytes from individuals homozygous and heterozygous for cystinosis’ opened a new era of research towards understanding the pathogenesis and finding treatments for cystinosis patients. His tremendous contribution transformed cystinosis from a fatal disorder of childhood to a treatable chronic disease, with a new generation of cystinosis patients being now in their 40th and 50th years. Dr. Schneider wrote a fascinating ‘Personal History of Cystinosis’ highlighting the major milestones of cystinosis research. Unfortunately, he passed away before this manuscript could be published. Fifty-five years after his first paper on cystinosis, the ‘Personal History of Cystinosis’ by Dr. Schneider is a tribute to his pioneering discoveries in the field and an inspiration for young doctors and scientists who have taken over the torch of cystinosis research towards finding a cure for cystinosis.

Helios gene gun particle delivery for therapy of acid maltase deficiency

Autosomal recessive deficiency of lysosomal acid maltase (GAA) or glycogen storage disease type II (GSDII) results in a spectrum of phenotypes including a rapidly fatal infantile disorder (Pompe's), juvenile, and a late-onset adult myopathy. The infantile onset form presents as hypotonia with massive accumulation of glycogen in skeletal and heart muscle, with death due to cardiorespiratory failure. Adult patients with the slowly progressive form develop severe skeletal muscle weakness and respiratory failure. Particle bombardment is a safe, efficient physical method in which high-density, subcellular-sized particles are accelerated to high velocity to carry DNA into cells. Because it does not depend on a specific ligand, receptor, or biochemical features on cell surfaces, particle-mediated gene transfer can be readily applied to a variety of systems. We evaluated particle bombardment as a delivery system for therapy of GSDII. We utilized a vector carrying the CMV promoter linked to the human GAA cDNA. Human GSDII cell lines (fibroblasts and lymphoid) as well as ex vivo with adult-onset peripheral blood cells (lymphocytes and monocytes) were transiently transfected by bombardment with a Helios gene gun delivering gold particles coated with the GAA expression plasmid. All cell types showed an increase in human GAA activity greater than 50% of normal activity. Subsequently, GAA -/- mice were treated every 2 weeks for 4 months by particle bombardment to the epidermis of the lower back and hind limbs. Muscle weakness in the hind and forelimbs was reversed. These data suggest that particle delivery of the GAA cDNA by the Helios gene gun may be a safe, effective treatment for GSDII.

Glycogenosis type II: a juvenile-specific mutation with an unusual splicing pattern and a shared mutation in African Americans

The recessively inherited deficiency of acid alpha-glucosidase (GAA) called Glycogenosis Type II is expressed as three different phenotypes: infantile, juvenile, and adult. At the molecular level, infantile and adult forms of the disease have been extensively studied, but little is known regarding the genetic defects associated with the juvenile form. We describe a novel mutation that defines the intermediate juvenile phenotype in a compound heterozygous patient. A transversion of t to g in intron 6 at position -22 creates a cryptic acceptor site and results in unusual splicing abnormality: insertion of 21 nucleotides of the intronic sequence into mRNA and removal of exon 6 without disruption of the reading frame. The second mutation, Arg854Stop in exon 18, had been previously identified in another African-American patient (Hermans et al., 1993a). Family study indicates that a silent allele harboring the Arg854Stop mutation in our patient is inherited from the patient's father, who is also African-American, thus suggesting a common mutation in this population.

Molecular cloning of a gene encoding acid alpha-glucosidase from Tetrahymena pyriformis

Lysosomal acid alpha-glucosidase is essential for the degradation of glycogen to glucose in lysosomes. The ciliated protozoan Tetrahymena pyriformis secretes acid alpha-glucosidase into its culture medium. We have earlier reported the purification and characterization of acid alpha-glucosidase from T. pyriformis. The exact molecular mechanism of secretion of this enzyme has not yet been clarified. In the present study we have isolated a full length cDNA clone encoding acid alpha-glucosidase from T. pyriformis. The isolated clone (3019 bp) contained an open reading frame encoding 923 amino acids, and has an estimated molecular mass of 104 kDa. Northern blot analysis revealed that the isolated cDNA hybridized to a 2.8-kb mRNA transcript. N-terminal amino acids after the first methionine fulfilled the requirement of a signal peptide. The deduced amino acid sequence contains the amino acid sequences determined of several peptides derived from the purified enzyme, and was found to have 34% identity and 45% similarity with that of human lysosomal enzyme, with 75% identity in the 16 amino acids at the proposed active site.

Acarbose is a competitive inhibitor of mammalian lysosomal acid alpha-D-glucosidases

Intraperitoneal injections (approximately 400 mg/kg of body weight) of acarbose, an inhibitor of acid (1----4)-alpha-D-glucosidase, perturb the metabolism of glycogen in the liver, resulting in excess storage of lysosomal glycogen. The metabolism of skeletal muscle glycogen was unaffected, suggesting that acarbose either does not enter the tissue or that the muscle alpha-D-glucosidase is not inhibited. The hydrolysis of maltose and glycogen by the acid alpha-D-glucosidases from rat liver, rat skeletal muscle, and human placenta was inhibited competitively by acarbose. Thus, the lack of effect of acarbose upon the metabolism of muscle glycogen is due to its inability to enter the tissue.

Modulation of enzymatic activities during spontaneous and induced differentiation in a human pancreatic adenocarcinoma cell line CAPAN-1

Different enzymatic activities were studied in the human pancreatic cancer cell line CAPAN-1 in order to analyze their relation to differentiation. Alkaline phosphatase (Alk Ph), acid phosphatase, aminopeptidase, dipeptidyl peptidase IV, acid and neutral alpha-glucosidases, and acid beta-galactosidase were present. Especially alkaline phosphatase, which we have found to be of the placental type isoenzyme, is being highly expressed. Spontaneous cell differentiation at confluence as well as differentiating agents: sodium butyrate and DMSO, modulated the levels of three enzymes: Alk. Ph., aminopeptidase, and acid alpha-glucosidase. The exposure of the cells to the differentiating agents amplified the modulations occurring during the spontaneous differentiation. Aminopeptidase and acid alpha-glucosidase were found to be induced by differentiation. Alk Ph specific activity was significantly increased by the spontaneous and the butyrate-induced differentiations; whereas DMSO exerted an opposite effect, probably related to its biphasic action on cell proliferation.

Biosynthesis of two components of human acid alpha-glucosidase

Two acid alpha-glucosidase components of different molecular sizes (80 and 71 kDa) were separated from human placenta by DEAE-cellulose chromatography. Their catalytic properties were similar, and they showed almost the same molecular structure with regard to immunological properties and carboxy-terminal sequences, although the amino acid composition, the total hexose content, and the circular dichroism spectra were different. The pulse-chase labeling acid alpha-glucosidase with [3H]leucine revealed a processing pathway from a 110 kDa precursor to a 95 kDa intermediate form, then finally to 80 and 71 kDa mature forms. However, the sequence of appearance was different between the two mature enzymes. The 80 kDa component appeared first after chase for 5 h, and then the 71 kDa component followed. Their amounts became equal at 2 to 4 days. When ammonium chloride or leupeptin was added to the culture medium after chase for 5 h, the 71 kDa component failed to appear and the 80 kDa component was not converted to 71 kDa. It is concluded that probably only a part of the 80 kDa component is processed to form the 71 kDa component, although another possibility that cannot be excluded is that these two components are converted independently from the common intermediate 95 kDa protein.

A simple differential immunoprecipitation assay of urinary acid and neutral alpha-glucosidases for glycogenosis II

A specific assay for acid alpha-glucosidase in urine was developed to facilitate the diagnosis of glycogenosis II. This enzyme activity was calculated as a difference between the alpha-glucosidase activities before and after immunoprecipitation with antiserum to acid alpha-glucosidase. Acid alpha-glucosidase accounted for 86% of the total activity in control urine. All the cases of various clinical types of glycogenosis II showed either a marked decrease or a complete deficiency of this enzyme activity. A marked decrease of acid alpha-glucosidase was demonstrated by immunoblotting of the urine from patients with late-onset forms of this disease. These results indicate that assays of urinary acid alpha-glucosidase by this immunological method are useful for detection of the various types of glycogenosis II.

Trial of a cysteine proteinase inhibitor, EST, in experimental chloroquine myopathy in rats

The administration of 50 mg/kg/day of chloroquine to rats for 8 weeks produced the chloroquine myopathy characterized by autophagic vacuole formation and increases in lysosomal enzymes, especially cathepsins B & L. Coadministration of 10 mg/kg/day of a potent cysteine proteinase inhibitor, EST, and chloroquine prevented the induction of the chloroquine myopathy. Rats already suffering from the chloroquine myopathy were treated with 10 mg/kg/day of EST together with chloroquine injections for 5 weeks and also recovered remarkably from the myopathy. Thus, EST may be beneficial for myopathies associated with autophagic vacuoles.

Subcellular distribution of acid alpha-glucosidase in fibroblasts and of antigenically cross-reactive material in Pompe's disease fibroblasts

From fibroblasts of two cases of Pompe's disease (acid alpha-glucosidase deficiency), one of the childhood type (RH-SF-1) and one of the adult type (RH-SF-2), and normal fibroblasts, antigenically cross-reactive material and acid alpha-glucosidase were immunoprecipitated and analysed by immunoelectrotransfer blotting. The acid alpha-glucosidase and antigenically cross-reactive material (which reacts with antibody raised against normal acid alpha-glucosidase) revealed a precursor form of molecular weight 97,000 and two major components of 79,000 and 76,000. When monensin was added to the fibroblast culture, the two major components of normal acid alpha-glucosidase were decreased, whereas the large molecular weight precursor was increased. On the other hand, the 97,000 molecular weight component of cross-reactive material in the Pompe's fibroblasts (RH-SF-1 and RH-SF-2) was only slightly increased on monensin treatment. The fibroblasts were pulse-chase labelled with [2-H3] mannose and 32Pi. The cross-reactive material and acid alpha-glucosidase were precipitated with anti acid alpha-glucosidase antibody, and after sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), fluorography was performed. The radiolabel of 3H in the cross-reactive material of RH-SF-1 and -2 was weak, and 32P in the cross-reactive material of both fibroblasts was very weak when compared with those of the acid alpha-glucosidase. The radiolabel of 32P in the cross-reactive material of RH-SF-1 was extremely weak. Immunofluorescence histochemistry revealed a granular localization of acid alpha-glucosidase in the normal fibroblast cytoplasm, and a diffuse distribution of cross-reactive material in the cytoplasm of RH-SF-1 and -2. Immuno-electron microscopic examinations showed a normal acid alpha-glucosidase localization on the inner side of the lysosomal membrane and also diffusely in the lysosome; when treated with monensin, it was present on the trans part of the Golgi apparatus. Antigenically cross-reactive material, however, was found in the cytoplasm and endoplasmic reticulum. Some lysosomal localization was observed sporadically. Even after monensin treatment, it was not demonstrated on the Golgi apparatus.

Identification of denatured enzyme proteins in sodium dodecyl sulfate polyacrylamide gels

A simple modification of the immunological sandwich method of Muilerman et al. for the identification of denatured enzyme proteins in sodium dodecyl sulfate-polyacrylamide gels is described, enabling the method to be used in principle for any enzyme whose activity is not inhibited by binding to antibodies. An immunological sandwich consisting of denatured enzyme, antibodies, and native enzyme is formed on a nitrocellulose filter blot of the gel, the filter is divided into strips, and each strip is tested for enzyme activity. The presence of enzyme activity serves to identify the region in the gel containing denatured enzyme protein. Experiments with human lysosomal alpha-glucosidase as a model system are described. The method was applied to identify a protein of Mr 125,000 as the main component with UDPgalactose pyrophosphatase activity in a partially purified preparation of the enzyme from rat liver.

Diagnosis of Pompe's disease using leukocyte preparations. Kinetic and immunological studies of 1,4-alpha-glucosidase in human fetal and adult tissues and cultured cells

Kinetic and immunological studies of 1,4-alpha-glucosidase show that the distribution of acid, renal and neutral alpha-glucosidase at pH 4.0 and 6.5 is as follows: in liver and cultured fibroblasts and amniotic fluid cells the activity at pH 4.0 is mainly due to the acid enzyme. Even at pH 6.5, the activity is largely due to the residual activity of the acid enzyme. In kidney and leukocytes, however, the activity by acid enzyme at pH 4.0 represents only 30-60% of the total activity and the remaining activity is from renal enzyme. At pH 6.5, the activity is almost exclusively of renal enzyme. Renal alpha-glucosidase has a higher affinity for maltose (Km, 0.8 mmol/l) than acid enzyme, however; for glycogen acid enzyme shows the highest affinity (20.7 g/l). There is no significant difference in the kinetic characteristics of alpha-glucosidase between fetal and adult tissues. In kidney, however, a relative increase in renal enzyme to acid enzyme with age is found, i.e. in fetal kidney the alpha-glucosidase activity at pH 4.0 is more than twice that at pH 6.5, whereas in adult kidney, the activity ratio at pH 4.0-6.5 is approximately 1. Antibodies for human liver acid alpha-glucosidase decrease the alpha-glucosidase activity in normal leukocytes by 22-75% at pH 4.0 (0.54-3.8 nmol/min per mg protein). The decrease is significantly lower in patients with Pompe's disease (0-0.11 nmol/min per mg protein) as well as in their parents and some siblings (0.15-0.70).

Demonstration of acid alpha-glucosidase in different types of Pompe disease by use of an immunochemical method

The nature of mutant acid alpha-glucosidase (AAG) in muscle was studied in 6 patients with Pompe disease, consisting of 2 each of the infantile, childhood and adult types. Anti-human liver AAG rabbit antibody prepared in the present study was confirmed to be monospecific by immunodiffusion, immunotitration and immunohistochemical methods. It was found by the immunodiffusion and enzyme immunoassay methods using this antibody that the mutation produced a normal amount of enzyme protein but the latter was an inactive form, suggesting structural gene mutation in 5 of the 6 cases. In the remaining childhood type case there was no detectable amount of enzyme protein, suggesting that the mutation causes a reduction in the amount of the enzyme protein or synthesis of unstable enzyme protein. Similarly, the enzyme activity of AAG was markedly reduced in all patients, but that of neutral alpha-glucosidase was the least reduced in the adult type, medium in the childhood type, and the most reduced in the infantile type.

Immunocytochemistry of lysosomal hydrolases and their precursor forms in normal and mutant human cells

The acid hydrolases alpha-glucosidase, beta-galactosidase, N-acetyl-beta-D-hexosaminidase, beta-glucocerebrosidase and cathepsin D were studied immunocytochemically in normal and mutant human cells using monoclonal and affinity-purified polyclonal antibodies. For light microscopy, Rhodamine or Fluorescein-labelled conjugates were used, and for electron microscopy protein A-gold conjugates were employed. With the double labelling procedure, it was found that in normal fibroblasts every lysosome contained all the enzymes studied. The method described also enabled us to demonstrate the presence or absence of mutant enzyme protein in fibroblasts derived from patients with a genetic lysosomal enzyme deficiency. Immunoreactive acid hydrolases or their precursor forms were found in the rough endoplasmic reticulum, the cisternae of the Golgi complex, Golgi associated vesicles and lysosomes. This is in agreement with the present concept that the Golgi complex plays an essential role in the processing and targeting of lysosomal enzymes.

Further studies of the structure of human placental acid alpha-glucosidase

Acid alpha-glucosidase has been purified from human placenta to a specific activity of approximately 6800, (4-methylumbelliferyl-alpha-D-glucoside as a substrate) or 55,400 mumol g-1 min-1 (glycogen or maltose as substrate). The purified enzyme gives rise to multiple protein bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), i.e., a major doublet of 82K and 69K , a minor doublet of 25K and 21K , and a faint band of 100K. All of the molecular weight species stained as glycoproteins with an intensity apparently proportional to their protein content, and were present in enzyme from individuals homozygous for the allozyme alpha-Glu 1. Isoelectric focusing revealed only enzymatically active proteins which, when analysed by SDS-PAGE, gave rise to multiple molecular weight species. Chromatography of I125-labeled, purified enzyme on Bio-Gel P-100 revealed only a radiolabeled, high-molecular-weight species which corresponded with enzyme activity. These findings suggest that, in the native state, the mature enzyme exists as a high-molecular-weight species, which is dissociable in SDS to several low-molecular-weight species. These results are consistent with reports that a 100K primary product of translation is post-translationally modified to yield polypeptides of lower molecular weights, and that all of the molecular species are absent in cells genetically deficient for acid alpha-glucosidase. The possibility that the low-molecular-weight (20- 25K ) protein bands in SDS-gels corresponded to a previously reported low-molecular-weight species generated by treatment with guanidine-HCl was investigated. The I125-labeled, purified acid maltase was dissociated by guanidine into two equal peaks of approximately 64K and 28K molecular weight. Surprisingly, both peaks, when analyzed on SDS-gels, yielded identical and equally intensely staining bands of 64K molecular weight. These results suggest that the mature acid alpha-glucosidase is made up of polypeptides which are bonded in the native state by at least two different types of interaction, one type which is dissociable in SDS and one type which is dissociable in guanidine but not in SDS. The nature and possible function of the 25K polypeptide generated only by guanidine-HCl remains to be determined.

Human liver lysosomal alpha-glucosidase modified by chemical galactosylation and isolation of specific antibodies

Human liver acid alpha-glucosidase (1,4-alpha-D-glucan glucohydrolase, EC 3.2.1.3) was modified with water soluble carbodiimide in the presence of p-aminophenyl-beta-D-galactopyranoside. The incorporation of the aminophenyl derivative of galactose into alpha-glucosidase caused some changes in the physiocochemical properties of the enzyme: a blue shift in the absorption maximum, an alteration of the total electric charge affecting electrophoretic mobility upon polyacrylamide gel electrophoresis, and acquisition of the ability to interact specifically with Ricinus communis agglutinin. At the same time, the 'galactosylated' enzyme possessed high stability and exhibited catalytic activity towards maltose. The Km values of the native and modified enzymes with maltose were 6 and 5 mM, respectively. p-Aminophenyl-beta-D-galactopyranoside residues incorporated in alpha-glucosidase and in other proteins were found to be antigenic determinants to which the pure antibodies were obtained.

Confirmation of the regional localization of the genes for human acid alpha-glucosidase (GAA) and adenosine deaminase (ADA) by somatic cell hybridization

We have confirmed the localization of human acid alpha-glucosidase (GAA) to 17q21----q25 and of adenosine deaminase (ADA) to 20q13----20qter by examination of hybrid clones derived from a fusion between a human cell line carrying a 17/20 balanced translocation (17pter----17q25::20q13----20qter;20pter-- --20q13::17q25----17qter) and a mouse line deficient in thymidine kinase. These hybrids were constantly maintained in HAT selective media in order to select for the presence of the human thymidine kinase gene on the intact chromosome 17 (17q21----22) or the 17/20 (17pter----17q25::20q13----20qter) translocation chromosome. We detected human GAA by rocket immunoelectrophoresis, using a heterologous antibody raised against human acid alpha-glucosidase. A clone which contained the 17/20 translocation and no intact chromosome 17 was still positive for GAA. This finding confirms the exclusion of GAA from 17q25----17qter reported by Nickel et al. (1982). Combined with earlier results (Weil et al. 1979), GAA can be assigned to 17q21----17q25. A clone which contained only the 17/20 translocation chromosome and no intact chromosome 20 contained ADA. This confirms the previous localization of ADA to 20q13.2----qter by gene dosage studies (Philip et al. 1980).

Glycogen storage diseases in animals and their potential value as models of human disease

Glycogen storage diseases (GSD) are inborn errors of glycogen metabolism. Of the eight human GSD types in which the enzymatic deficiency has been identified, spontaneous animal counterparts have been reported for GSD I (glucose-6-phosphatase deficiency) in the mouse, for GSD II (acid alpha-glucosidase deficiency) in the dog, in cattle and in the quail, for GSD III (debrancher enzyme deficiency) in the dog and for GSD VIII (phosphorylase kinase deficiency) in the rat and the mouse. Experimentally induced GSD-like conditions have been described in the rat (Acarbose-induced GSD II-like conditions, iodoacetate-induced symptoms of myophosphorylase (GSD V) and myophosphofructokinase (GSD VII) deficiency) and the chicken (ochratoxin A-induced symptoms of cyclic AMP-dependent protein kinase deficiency). Enzymatic defects that are typical of the human GSD types have not been clearly identified in the induced animal conditions. The homology of animal and human GSD types is discussed. It is concluded that clinical, pathogenic and therapeutic studies of GSD may benefit from the use of animal models. For genetic studies of human GSD these models may prove to be of limited value, as the picture of several human GSD types is already obscured by genetic heterogeneity.

Biosynthesis of acid alpha-glucosidase in late-onset forms of glycogenosis type II (Pompe's disease)

Cultured human skin fibroblasts from control persons and from patients with the generalized and late-onset forms of Pompe's disease were labelled with radioactive leucine and the incorporation of radioactivity into acid alpha-glucosidase and cathepsin D was analysed by immunoprecipitation, gel electrophoresis and fluorography. When the labelling was carried out for 6-12 h in the presence of NH4Cl, the labelling of secreted alpha-glucosidase relative to that of secreted cathepsin D in fibroblasts from patients with the late-onset form of Pompe's disease was less than 15% of that in fibroblasts from control persons. However, when the fibroblasts were labelled for less than 1 h, the relative rate of incorporation of radioactivity into acid alpha-glucosidase was rather similar in the two types of fibroblasts. In fibroblasts from patients with the generalized form of Pompe's disease no incorporation of radioactivity into acid alpha-glucosidase could be detected.

Extension of human acid alpha-glucosidase polymorphism by isoelectric focusing in polyacrylamide gel

1. A method to analyse acid alpha-glucosidase (GAA) activity in human tissues by flatbed polyacrylamide gel isoelectric focusing has been devised. 2. With this method the GAA polymorphism has been extended from three to six commonly occurring phenotypes. 3. After isoelectric focusing the GAA2 isozyme migrated cathodally with respect to the GAA1 isozyme, whereas with the previous starch-gel electrophoresis method their relative positions were reversed. 4. The six common phenotypes are generated by three alleles, GAA*1, GAA*2 and GAA*4 with frequencies of 0.91, 0.03 and 0.06, respectively.

Skeletal-muscle alpha-glucosidases in bovine generalized glycogenosis type II

The skeletal muscle of cattle suffering from generalized glycogenosis type II was shown to lack acid alpha-glucosidase (EC 3.2.1.3) activity. Furthermore, there was no evidence of enzymically inactive proteins that cross-reacted with antibodies raised against acid alpha-glucosidase from the muscle of normal animals.

Characterization of neutral isozymes of human alpha-glucosidase: differences in substrate specificity, molecular weight and electrophoretic mobility

We have previously defined two isozymes of neutral alpha-glucosidase (alpha-D-glucoside glucohydrolase, EC 3.2.1.20) on the basis of differences in electrophoretic mobility and designated these neutral alpha-glucosidase AB and alpha-glucosidase C (Swallow, D.M., Corney, G., Harris, H. and Hirschhorn, R. (1975) Ann. Hum. Gen. 38, 391-406). We now describe differences between the two isozymes with respect to molecular weight, solubility in (NH4)2SO4, glycosylation, isoelectric point and substrate specificities. Neutral alpha-glucosidase C is precipitable in 40-60% (NH4)2SO4, has a molecular weight of 92 000, an isoelectric point of 5.5 and releases glucose from glycogen as well as from low molecular weight artificial and natural substrates containing alpha 1-4 glucosidic linkages. Neutral alpha-glucosidase AB precipitates at 0-40% (NH4)2SO4, binds to concanavalin A, has a molecular weight of greater than 150 000, and does not utilize alpha 1-4 linked glucose substrates larger than a disaccharide. Neutral alpha-glucosidase AB migrates more rapidly to the anode than alpha-glucosidase C when agarose, Cellogel, acrylamide or starch are used as support media. Both isozymes are equally inhibited by Zn2+.

Morquio's disease type A: absence of material cross reacting with antibodies against N-acetylgalactosamine-6-sulfate sulfatase

An antiserum was raised in guinea pigs against purified normal human N-acetylgalactosamine-6-sulfate sulfatase, the enzyme affecting in Morquio's disease type A. The antiserum precipitated most of N-acetylgalactosamine-6-sulfate sulfatase from a concentrate of normal human urine. The antigen-antibody complex was enzymatically active. Urine concentrates from five patients with Morquio's disease type A did not contain material competing with the normal enzyme for binding to soluble or Sepharose-bound antibodies. No precipitin arc was obtained on immunodiffusion of antiserum and urine from the single patient investigated by this method. From the sensitivity of the indirect immunoassay it was concluded that the urine of the five patients contained less than 5% of the normal amount of cross-reacting material.

Uncommon case of type II glycogenosis

The authors report an uncommon case of type II glycogenosis. An 8-year-old boy developed a slow progressive myopathy. Biopsy of skeletal muscle showed scarce lesions under the optic microscope but in 50% of the fibers the presence of vacuoles filled with glycogen under the electron microscope. Ultrastructural analysis of fibroblasts in culture showed numerous vacuoles filled with glycogen, characteristic of type II glycogenosis. Enzymatic analysis revealed that acid-alpha-glucosidase activity was normal in muscle tissues but deeply deficient in leukocytes and fibroblasts in culture. This is, as far as we know, the first case with such a discrepancy in the distribution of the enzymatic activity, and it underlines the necessity of investigating several tissues in atypical cases.

Carbohydrate content of acid alpha-glucosidase (gamma-amylase) from human liver

The presence of carbohydrates in homogeneous preparations of human liver acid alpha-glucosidase has been established and the carbohydrate content of the enzyme determined. The enzyme was purified with the specific purpose of removing all low-molecular-weight carbohydrates. It was specifically adsorbed on Concanavalin A-Sepharose, eluted with methyl-alpha-D-mannopyranoside and gave a positive reaction with the phenol-sulphuric acid reagent. These facts taken together provide evidence that the enzyme studied is a glycoprotein. The analysis of the carbohydrate content of human liver acid alpha-glucosidase showed that there were 8.3 glucosamine, 13.2 mannose and possibly 3--4 glucose residues per molecule of the enzyme with a molecular weight of 98,000.

Use of immobilized antibodies in investigating acid alpha-glucosidase in urine in relation to Pompe's disease

(1) A simple method is described for the isolation of the lysosomal enzyme, acid alpha-glucosidase (alpha-D-glucoside glucohydrolase, EC 3.2.1.20) from normal human liver. Antibodies raised against the purified enzyme were immobilized by covalent coupling to Sepharose 4B. (2) Acid alpha-glucosidase can be quantitatively removed from normal urine by incubating with an excess of immobilized antibody. With p-nitrophenyl-alpha-glucoside as substrate, acid alpha-glucosidase accounts for 91 +/- 3% of the total alpha-glucosidase activity at pH 4.0 IN Normal urine. (3) In urine from a patient with the infantile form of Pompe's disease ('acid maltase deficiency'), no alpha-glucosidase activity could be removed by the immobilized antibody, in agreement with the fact that acid alpha-glucosidase is absent in these patients. (4) In urine from patients with the late-onset form of Pompe's disease, 46 +/- 11% of the alpha-glucosidase activity at pH 4.0 can be removed by incubation with immobilized antibodies, indicating that residual acid alpha-glucosidase activity is present in urine of these patients. The residual acid alpha-glucosidase activity amounts to about 5% of that in the urine of control persons. (5) If acid alpha-glucosidase is adsorbed to immobilized antibodies, the activity can still be measured with p-nitrophenyl-alpha-glucoside as substrate. The Km for p-nitrophenyl-alpha-glucoside is not significantly changed by adsorbing purified acid alpha-glucosidase to immobilized antibodies. (6) The properties of acid alpha-glucosidase from urine of patients with late-onset Pompe's disease were compared with those of acid alpha-glucosidase from normal urine, both adsorbed to immobilized antiserum. The pH-activity profile of the enzyme from urine of patients with late-onset Pompe's disease can not be distinguished from that of the normal urinary enzyme. The Km for p-nitro-phenyl-alpha-glucoside of the two enzymes is identical, both at pH 4 and 3. The titration curves of the two enzymes with immobilized antibodies are identical.

Separation of acid and neutral alpha-glucosidase isoenzymes from fetal and adult tissues, cultivated fibroblasts and amniotic fluid cells by DEAE-cellulose and sephadex G-100 column chromatography

Isoenzymes of alpha-glucosidases (EC 3.2.1.20) from various human organs and body fluids from fetuses and adults were separated by DEAE-cellulose column chromatography and gel filtration using Sephadex G-100. A minicolumn (0.35 X 2.5 cm) was used for the DEAE-cellulose column chromatography of extracts from tissues as well as cultivated cells of skin fibroblasts and amniotic fluid. The enzyme activity in the eluates was measured by the use of a methylumbelliferyl derivative as substrate and a very sensitive Microscope fluorimeter. In most tissue samples alpha-glucosidase was eluted mainly as a single peak when monitored at acid pH and as two peaks when the activity was measured at neutral pH in both columns. Another small peak representing alpha-glucosidase was found in fresh extracts of cultured cells on DEAE-cellulose columns. Neutral alpha-glucosidase especially in fibroblasts was extremely sensitive to storage at -20 degrees C. DEAE-cellulose column chromatography of plasma and amniotic fluid showed similar elution patterns of alpha-glucosidase. Differences were noticed in the elution pattern of urine from infants and adults. The tissue distribution and the different characteristics of the enzyme in samples of various origins and ages were discussed.

Metabolism of hydrogenated palatinose, an equimolar mixture of alpha-D-glucopyranosido-1,6-sorbitol and alpha-D-glucopyranosido-1,6-mannitol

Hydrogenated palatinose, an equimolar mixture of alpha-D-glucopyranosido-1,6-sorbitol and alpha-D-glucopyranosido-1,6-mannitol, was investigated as a potential oral sugar substitute in the following experiments in man and rat. 1. Enzymatic cleavage occurred at slow rates by maltase (alpha-glucosidase) of jejunal mucosa, liver lysosomes and yeast. 2. Part of ingested hydrogenated palatinose arrived unsplit at the caecum of the rat and underwent fermentation there; excretion in feces and urine are neglegible in man and rat. 3. Growth and maintenance of rats demonstrated 20--40 percent diminished caloric utilisation of diets containing 34.5 percent hydrogenated palatinose whereas indirect calorimetry in man showed about 50 percent caloric deficit. 4. Blood sugar did not increase in man after oral doses up to 100 g. 5. The capacity of the rat kidneys for excretion of hydrogenated palatinose and its constituents was high, symptoms of incompatibility were not observed.

Adult-onset acid maltase deficiency: a postmortem study

In a postmortem study of a patient with adult-onset acid maltase deficiency (AMD), morphological abnormalities were confined to skeletal muscle and consisted of a vacuolar myopathy. Acid maltase activity, however, was approximately 6% of normal in muscle, liver, and brain, and 3% of normal in heart. Kinetic characteristics, and inhibition by antibodies and Zn++, showed that the residual activity was "authentic" acid maltase. Neutral maltase activity was normal in muscle and liver, but decreased in brain (55% of normal) and heart (19% of normal). Although the relative decrease of acid maltase was similar in different tissues, absolute residual activity was lowest in skeletal muscle: this may explain the selective involvement of this tissue in late-onset AMD.

Some properties of human liver acid alpha-glucosidase

1. Albumin activates human liver acid alpha-glucosidase (alpha-D-glucoside hydrolase, EC 3.2.1.20). From the Arrhenius plot, pH-dependence and Lineweaver-Burk plots it can be concluded that this activation is not only due to stabilisation of the enzyme, but also influences the enzymatic activity. It is proposed that for optimal functioning human liver acid alpha-glucosidase needs a protein environment. 2. Glycogen has a competitive inhibitory effect on the hydrolysis of 4-methylumbelliferyl-alpha-D-glucopyranoside, in contrast to maltose which exhibits a non-competitive type of inhibition. It is concluded that two catalytic sites exist, one for glycogen and one for maltose, while both sites influence each other. With glycogen as substrate a break in the Arrhenius plot is found. This is not the case when maltose is used as substrate. 3. The effect of antibody raised against human liver acid alpha-glucosidase on the activity of human liver acid alpha-glucosidase is studied. No corss-reacting material could be demonstrated in the liver of a patient with glycogen storage disease Type II (M. Pompe, acid alpha-glucosidase deficiency).

A serological investigation into the acidic alpha-D-mannosidase in normal Angus cattle and in a calf with mannosidosis

Antiserum was raised in a rabbit against bovine kidney acidic alpha-mannosidase that had been purified 570-fold by affinity chromatography on concanavalin A--Sepharose and Sepharose 4B-xi-aminohexanoylmannosylamine. The antiserum precipitated the acidic but not the neutral alpha-mannosidase in normal calf tissues. Human acidic alpha-mannosidase cross-reacted partially with the antiserum, emphasizing the close structural resemblance between the enzyme in the two species. The residual acidic alpha-mannosidase in the tissues of a calf with mannosidosis was also precipitated by the antiserum, the same volume of antiserum being required to precipitate a unit of alpha-mannosidase activity from the normal and pathological tissues. The concentration of cross-reacting material detected by antibody-consumption experiments in the organs of the calf with mannosidosis appeared to be proportional to the concentration of the residual acidic alpha-mannosidase. It is suggested that the residual acidic alpha-mannosidase in mannosidosis accounts for the cross-reacting material detected and that it is unlikely that enzymically inactive but cross-reacting material is present. The residual acidic alpha-mannosidase could be a decreased concentration of the normal gene product or an altered enzyme with a decreased specific enzymic activity and a correspondingly decreased antigenicity.

Acid maltase deficiency (type II glycogenosis). Morphological and biochemical study of a childhood phenotype

Pathological and biochemical data are reported on a 4(4)/12-year-old male patient with a severe myopathic disorder, hepatomegaly, recurrent pulmonary infections ending fatally. Combined morphological and enzymatic studies on muscle biopsy led to the diagnosis of acid maltase deficiency (Type II glycogenosis). On post mortem examination, lysosomal glycogen storage is found in skeletal muscles and liver, while heart and central nervous sytem are spared. Both hydrolytic and transferase activities of acid maltase are absent in cultured fibroblasts, heart, liver and postmortem skeletal muscles. That in the biopsied skeletal muscle only, the transferase activity alone is deficient while the hydrolytic function is maintained at low normal levels correlates well with the abnormal structure of the glycogen stored in that muscle. However, these findings on biopsied muscle cannot be reconciled with the absence of both functions and the presence of normal glycogen in other biopsied tissues or in postmortem specimens from the same patient.

Acid maltase deficiency in non-identical adult twins. A morphological and biochemical study

Acid maltase deficiency is described in non-identical adult twins. The onset of the disease can be traced into late infancy; the clinical picture is one of severe muscular dystrophy; respiratory insuficiency was the cause of death in one case. The autopsy showed the central nervous system, heart and liver to be spared. Glycogen filled vacuoles are found in skin, mesenchymal cells, small nerves and skeletal muscles. The light microscopic study of 9 different muscles showed extremely variable involvement ranging from normal appearance to overt vacuolization. A 6--20% residual acid alpha-glucosidase activity was found in visceral organs, cultured fibroblasts and in some skeletal muscles. No satisfactory explanation can be given why this generalized acid alpha-glucosidase deficiency produces a selective involvement of skeletal muscles. If compared with infantile AMD (Pompe's disease) our cases have a much higher residual acid alpha-glucosidase activity and show the presence of an antigenically detectable protein. From our study and from a similar report in the literature (de Barsy et al., 1975), it appears that a combined approach of light microscopy, electron microscopy and biochemical analysis (determination of acid alpha-glucosidase) is necessary to make a diagnosis of AMD in adults.

Partial purification and characterization of alpha-glucosidase from Pseudomonas fluorescens W

The alpha-glucosidase (alpha-D-glucoside glucohydrolase, EC 3.2.1.20) of Pseudomonas fluorescens W was partially purified by (NH4)2SO4 fractionation, Sephadex G-200 and DEAE-cellulose column chromatography. The enzyme showed great specificity for maltose hydrolysis, with very little action against polymeric forms. Sucrose, isomaltose, alpha-methylglucoside, and maltobionic acid were not hydrolyzed. Turanose was a strong competitive inhibitor, and glucose a weaker one. Tris (2-amino-2-hydroxymethylpropan-1:3-diol) inhibited enzyme activity significantly only at alkaline pH. Mercuric, cupric, and silver cations strongly inhibited, and EDTA (ethylenediaminetetraacetate) weakly inhibited the enzyme. The isolated enzyme was rather unstable even at 4 degrees C, and was destroyed by freezing and lyophilization. Inositol and albumin had a slightly protective effect. Sulfhydryl-binding reagents strongly inhibited the enzyme.

Physico-chemical and immunological properties of acid alpha-glucosidase from various human tissues in relation to glycogenosis type II (Pompe's disease)

The physico-chemical and immunological properties of acid alpha-glucosidase from various human tissues have been studied. Heat stability of acid alpha-glucosidase from heart, liver and skeletal muscle is identical, but for kidney some different results are obtained. Identical isoelectrofocussing patterns are found for heart, liver and skeletal muscle. Furthermore, the effect of antiserum against human liver acid alpha-glucosidase on the activity of acid alpha-glucosidase from various tissues is studied. The results are discussed in relation to glycogenosis type II (Pompe's disease).

Sanfilippo disease type B: presence of material cross reacting with antibodies against alpha-N-acetylglucosaminidase

1. alpha-N-Acetylglucosaminidase, the enzyme deficient in Sanfilippo disease type B (mucopolysaccharidosis III B) was purified from normal human urine. An antiserum was raised in rabbits against the purified enzyme. Preincubation of the antiserum with crude alpha-N-acetylglucosaminidase from normal human urine, followed by centrifugation, led to a marked reduction of the enzyme activity in the supernatant. Formation of the antibody-enzyme complex had no influence on the activity. The thermal stability of the enzyme was markedly enhanced by complex formation with the antiserum. 2. In the urine from three patients with Sanfilippo disease type B the presence of cross-reacting material could be demonstrated by incubating the antiserum with alpha-N-acetylglucosaminidase in the presence of Sanfilippo B urine or by pretreatment of the antiserum with Sanfilippo B urine. 3. Immunodiffusion and immunoelectrophoresis of crude normal or Sanfilippo B urine gave rise to up to four precipitation lines, only one of which exhibited alpha-N-acetylglucosaminidase activity in the case of normal urine. Purified alpha-N-acetylglucosaminidase yielded only a single precipitation line. After adsorption with the purified enzyme the antiserum did not cross react with any of the urinary proteins. 4. On a quantitative determination of cross-reacting material using Sepharose immobilized antibodies in the urine from two Sanfilippo B patients the amount of cross-reacting material appeared to be less than one fourth of the amount of alpha-N-acetylglucosaminidase protein in an age-matched control urine. The cross-reacting material present in the urine of Sanfilippo B patients had a significant lower binding affinity for antibodies against alpha-N-acetylglucosaminidase than preparations from normal human urine. Taking into account this lower binding affinity, it can be calculated that the amount of cross-reacting material in the urine of Salfilippo B patients exceeds that of normal controls. 5. It is concluded that Sanfilippo disease type B is due to a mutation of a structural gene coding for alpha-N-acetylglucosaminidase. The mutation affects the catalytical and immunological properties of the enzyme protein.