Lack of an alpha-1,4-glucan: alpha-1,4-glucan 6-glycosyl transferase in a case of type IV glycogenosis

A mild juvenile variant of type IV glycogenosis

The mild juvenile form of type IV glycogenosis, confirmed by a profound deficiency of the brancher enzyme in tissue specimens is reported from three Turkish male siblings who, foremost, suffered from chronic progressive myopathy. Muscle fibers contained polyglucosan inclusions of typical fine structure i.e. a mixture of granular and filamentous glycogen. They reacted strongly for myophosphorylase, but were resistant to diastase. These inclusions were ubiquitinated and reacted with antibody KM-279 which previously has been shown to bind to Lafora bodies, corpora amylacea and polyglucosan material in hepatic and cardiac cells of type IV glycogenosis as well as polyglucosan body myopathy without brancher enzyme deficiency. Our findings confirm that although rate, a mild form of type IV glycogenosis is marked by polyglucosan inclusion not only in myofibers, but also in smooth muscle and sweat gland epithelial cells. This further implies that when polyglucosan inclusions are observed within myofibers it is mandatory to examine the muscle tissue for brancher enzyme activity since the brancher enzyme activities in circulating erythrocytes and leucocytes were normal in all three affected siblings and their parents. Therefore, it can be concluded that the patients reported on here represent a variant form of type IV glycogenosis, in which the defect is limited to muscle tissue. This further indicates that there are several different types of type IV glycogenosis with variable clinical manifestations.

Hereditary branching enzyme dysfunction in adult polyglucosan body disease: a possible metabolic cause in two patients

We describe 2 unrelated patients with adult polyglucosan body disease (APBD) diagnosed by sural nerve biopsy. Both patients were offspring of consanguineous marriages. They presented clinically with late onset pyramidal tetraparesis, micturition difficulties, peripheral neuropathy, and mild cognitive impairment. Magnetic resonance imaging of the brain revealed extensive white matter abnormalities in both. In search of a possible metabolic defect, we evaluated glycogen metabolism in these patients and their clinically unaffected children. Branching enzyme activity in the patients' polymorphonuclear leukocytes was about 15% of control values, whereas their children displayed values of 50 to 60%, suggesting a possible autosomal recessive mode of transmission. This is the first report of an inherited metabolic defect in patients with adult polyglucosan body disease. We suggest that branching enzyme dysfunction may be implicated in the pathogenesis of some patients with adult polyglucosan body disease.

Apparent absence of glycogen branching enzyme activity in phosphofructokinase deficiency

A 30-year-old woman with clinical features and biochemical findings of muscle phosphofructokinase deficiency was found to have a very low level of alpha-1,4-glucan:alpha-1,4-glucan-6-transglucosylase (branching enzyme, EC 2.4.1.18) activity in muscle. In contrast, branching enzyme activity in the leukocytes was in the range of control values. After sedimentation of the glycogen from muscle homogenates by centrifugation at 105,000 g, branching enzyme activity in muscle of the patient was similar to that of control subjects. This patient illustrates the possibility of falsely diagnosing branching enzyme deficiency when muscle glycogen content is elevated. It is likely that such an artefact may also cause a false positive diagnosis of branching enzyme deficiency in other metabolic diseases associated with glycogen accumulation.

Branching enzyme activity of cultured amniocytes and chorionic villi: prenatal testing for type IV glycogen storage disease

Although type IV glycogen storage disease (Andersen disease; McKusick 23250) is considered to be a rare, autosomally recessive disorder, of the more than 600 patients with glycogenosis identified in our laboratory by enzymatic assays, 6% have been shown to be deficient in the glycogen branching enzyme. Most of the 38 patients with type IV glycogen storage disease who are known to us have succumbed at a very early age, with the exception of one male teenager, an apparently healthy 7-year-old male, and several 5-year-old patients. Fourteen pregnancies at risk for branching enzyme deficiency have been monitored using cultured amniotic fluid cells, and four additional pregnancies have been screened using cultured chorionic villi. Essentially no branching enzyme activity was detectable in eight samples (amniocytes); activities within the control range were found in five samples (three amniocyte and two chorionic villi samples); and five samples appeared to have been derived from carriers. In two of the cases lacking branching enzyme activity, in which the pregnancies were terminated and fibroblasts were successfully cultured from the aborted fetuses, no branching enzyme activity was found. Another fetus, which was predicted by antenatal assay to be affected, was carried to term. Skin fibroblasts from this baby were deficient in branching enzyme. Pregnancies at risk for glycogen storage disease due to the deficiency of branching enzyme can be successfully monitored using either cultured chorionic villi or amniocytes.

A new variant of type IV glycogenosis: deficiency of branching enzyme activity without apparent progressive liver disease

Type IV glycogenosis is due to branching enzyme deficiency and is usually manifested clinically by progressive liver disease with cirrhosis and hepatic failure between the second and fourth years of life. We describe a 5-year-old boy who, following an acute febrile illness at 2 years of age, was first noted to have hepatomegaly with mildly elevated serum transaminase levels. Liver biopsy revealed hepatic fibrosis with periodic-acid Schiff-positive, diastase-resistant inclusions in hepatocytes and fibrillar inclusions characteristic of amylopectin by electron microscopy. Enzymatic assay revealed deficient hepatic branching enzyme activity with normal activity of glucose-6-phosphatase, debranching enzyme and phosphorylase activities. During the succeeding 3 years, he grew and developed normally with apparent resolution of any clinical evidence of liver disease and only intermittent elevation in serum transaminase levels associated with fever and prolonged fasting. Repeat liver biopsy at 4 years of age showed persistence of scattered hepatocellular periodic-acid Schiff-positive, diastase-resistant inclusions, but no progression of hepatic fibrosis in spite of persistent deficiency of hepatic branching enzyme activity. Skeletal muscle and skin fibroblasts from the patient also showed deficient enzyme activity. Skin fibroblasts from both parents exhibited half the normal control activity, suggesting a heterozygote state. This is the first documented patient with deficiency of branching enzyme but without evidence of progressive hepatic disease. This patient, coupled with reports of other patients with late onset hepatic or muscle disease with branching enzyme deficiency, suggests that the defect resulting in Type IV glycogen storage disease is more heterogenous and possibly more common than previously suspected.

Severe cardiopathy in branching enzyme deficiency

A 7 1/2-year-old girl had exercise intolerance and exertional dyspnea. Four months later, congestive heart failure developed, with recurrent chylous pleural effusions, and she died at age 8 1/2 years. Endomyocardial biopsy tissue showed abundant PAS-positive, diastase-resistant cytoplasmic deposits. Similar inclusions were seen in muscle, skin, and liver specimens. Postmortem studies showed that the abnormal polysaccharide was especially abundant in heart and muscle, but was also present in all other tissues, including the central nervous system. Glycogen isolated from heart, muscle, and spinal cord showed a shift of the iodine spectrum toward higher than normal wavelengths. Branching enzyme activity was lacking in the muscle biopsy specimen and in all postmortem tissues; glycogenolytic enzymes had normal activities. These studies show that cardiomyopathy can be the first symptom of generalized branching enzyme deficiency and that the degree of accumulation of the abnormal polysaccharide may vary in different tissues.

A juvenile variant of glycogenosis IV (Andersen disease)

An unusual patient with Andersen disease (glycogenosis type IV) is presented, with only relatively mild clinical symptoms at the age of 8 years. The patient has a profound deficiency of glycogen-branching enzyme.

Myopathies due to enzyme deficiencies

After the discovery in 1959 of myophosphorylase deficiency, at least 15 myopathies due to deficiency of enzymes involved in energy substrate utilization have been described. In this review two main categories of enzymopathies, glycogenosis and mitochondrial disorders, are discussed. Clinically, the patients with these categories of enzyme defects present two major syndromes: acute recurrent muscle impairment, generally related to exercise, associated with cramps and/or myoglobinuria; progressive muscular weakness and wasting eventually associated with signs of affected organs other than skeletal muscle. Defects of glycogen breakdown and of the first step of glycolysis are more frequently associated with acute exercise intolerance, such as in myophosphorylase and phosphofructokinase deficiencies, but may be associated with progressive muscle weakness and wasting, such as in acid maltase and debrancher enzyme deficiency. Clinical heterogeneity is common in these disorders, but a biochemical explanation for their different clinical expression is still lacking. Defects of the second step of glycolysis, phosphoglycerate kinase, phosphoglycerate mutase and lactate dehydrogenase deficiencies, have been discovered recently and are associated with exercise intolerance. The reason for muscle weakness and atrophy in glycogenosis is still unclear, although it has been suggested that excessive protein catabolism occurs in myophosphorylase, debrancher and acid maltase deficiencies. Myopathies due to deficiencies of mitochondrial enzymes are less well defined, as a group, than the glycogenoses. They are currently considered to fall into three main groups: defects of substrate utilization, such as carnitine palmitoyltransferase deficiency; defects of respiratory chain complexes, such as cytochrome-c-oxidase deficiency and defects of phosphorylation-respiration coupling, such as Luft's disease. Again, severe and benign exercise intolerance or progressive life-threatening myopathic syndromes may be the clinical expression of these disorders. Detailed biochemical and morphological studies of muscle biopsies are needed in these patients to obtain a definite diagnosis and prognosis, and to decide on eventual treatment.

Soluble starch synthases and starch branching enzymes from cotyledons of smooth- and wrinkled-seeded lines of Pisum sativum L

Soluble starch synthase and branching enzyme were purified from 18-day-old cotyledons of the smooth-seeded pea cultivar Alaska (RR) and wrinkled-seeded pea cultivar Progress #9 (rr) by DEAE-cellulose chromatography. Two coeluting peaks of primed and citrate-stimulated starch synthase activity and a major and minor peak of branching enzyme activity were observed in Alaska. However, in Progress #9, only one peak of synthase activity was found. When crude extracts of Progress #9 were centrifuged, over 70% of the starch synthase activity was recovered in the pelleted fraction, and additional washings of the pellet released no further activity. The addition of purified starch granules to Alaska crude extracts also resulted in the recovery of a greater proportion of synthase activity in pelleted fractions. The two peaks of branching enzyme activity in Alaska differed in their stimulation of phosphorylase, amylose branching activity, and activity in various buffers. The DEAE-cellulose profile of Progress #9 showed no distinct peak of branching enzyme and less than 10% of the total activity found in Alaska. The association of one form of soluble starch synthase with the pelleted fraction and the greatly reduced levels of branching enzyme provide a partial explanation for the appearance of high-amylose starch in Progress #9 cotyledons.

Purification and subunit structure of glycogen-branching enzyme from rabbit skeletal muscle

1,4-alpha-glucan:1,4-alpha-glucan 6-alpha-D-(1,4-alpha-D-glucano) transferase (branching enzyme) was purified by ammonium sulphate precipitation, chromatography on DEAE-cellulose, fractionation with poly(ethyleneglycol) 6000, chromatography on DEAE-Sepharose and gel filtration on Sephadex G150. The final specific activity was 3000 U/mg corresponding to a purification of approximately 10000-fold over the muscle extracts. 0.6 mg of enzyme was isolated from 4000 g muscle within eight days corresponding to an overall yield of 7%. The purified protein was homogeneous as judged by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate, and this technique yielded a molecular weight of 77000 for the subunit molecular weight of branching enzyme. The apparent molecular weight of the native enzyme determined by gel filtration on Sephadex G150 was 60000, demonstrating that branching enzyme is a monomeric protein. Only a very small proportion of the branching enzyme activity in muscle extracts (2%) precipitated with the protein-glycogen complex. This finding, and its low concentration in muscle, explain why a protein-staining band corresponding to branching enzyme cannot be detected by polyacrylamide gel electrophoresis of the protein-glycogen complex.

Type IV glycogenosis - a study of two cases

Liver biopsy materials of two siblings with type IV glycogenosis were studied by light and electron microscopy. Biochemical analysis was added using autopsy material in one of the two cases. Two kinds of polysaccharides were noted not only in the cardiac muscle, skeletal muscles, smooth muscles and reticuloendothelial cells, but also in the neutrophils and platelets. One was glycogen and the other was similar to amylopectin. Ultrastructurally, a large amount of fibrils, 60 A in width, glycogen rosettes and glycogen granules were detected in those cells. Branching glycosyltransferase deficiency was biochemically confirmed in one case examined.

Enzymic explorations of the structures of starch and glycogen

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