D-2-Acetamido-2-deoxyhexosidases

Frendsdoiff, and E. Galun, Arch. Mikrobioi, 1976,108, 9. 

Chibata, M. Furui, K. Yamashita, and A. Sumi, Biotechnol. and Bioeng., 1975, 17, 1797. 

Likhtenshtein, Spin Labelling Methods in Molecular Biology , Wiley, Chichester, 197 

Anti-(a-foetoprotein) antibody KTA - Azotobacter vinelandii) antibody 

Anti- Phaseolus vulgaris a-D-mannosidase I) antibody immunoglobulin IgG 

2 j3-D-2-Acetamido-2-deoxygalactosidases, /3-D-2-Acetamido-2-deoxyglucosidases, and 3-D-2-Acetamido-2-deoxyhexosidases 

Intravenously administered I-labelled human j3-D-2-acetamido-2-deoxyhexo-sidase A was rapidly cleared from the circulation of rats and accumulated in the 

Lloyd and P. A. Griffths, Lysosomes in Applied Biology and Therapeutics , vol. 6, North Holland Publishing Co., Amsterdam, 1979, p. 517. 

Kennedy and C. A. White, in Comprehensive Organic Chemistry , Pergamon, Oxford, 1979, p. 755. 

Potier, J. Teitelbaum, S. B. Melancon, and L. Dallaire, Biochem. Biophys. Acta, 1979, 566, 80. 

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These findings have been substantiated by the observation that the selective hepatic uptake of the lysosomal glycosidase 3-D-2-acetamido-2-deoxyhexosidase, which is a glycoprotein with terminal D-mannosyl residues, is by the sinusoidal cells. ... 

A search for lysomal hydrolases and related enzymes has been made in haemolysates from human and rabbit red cells.Apart from acid phosphatases, significant activities were found only for a-D-mannosidase, neutral a-D-glucosidase, and j3-D-2-acetamido-2-deoxyhexosidase. 

A comparative study of the properties of human and rat 3-D-2-acetamido-2-deoxyhexosidases has been reported. There are four j3-D-2-acetamido-2-deoxy-hexosidases isoenzymes in rat serum one is thermostable and the remaining three are thermolabile. Human serum contains three isoenzymes two are thermostable and one is thermolabile. In general, the /3-D-2-acetamido-2-deoxy-hexosidases isoenzymes in rat serum are more thermolabile than those in human serum. In contrast, the kinetic properties of the j8-D-2-acetamido-2-deoxyhexo-sidase isoenzymes in serum from the two species are similar. Rat liver and human placenta contain two 3-D-2-acetamido-2-deoxyhexosidase isoenzymes, one of which is thermolabile and the other thermostable. These tissue isoenzymes from the two species have similar physical and kinetic properties. 

L-Thyroxine has been shown to evoke an increase in j3-D-2-acetamido-2-deoxyhexosidase activity in adult rat liver. This increase occurred solely in the form of A-like heat labile components of the activity, the activity of the form B-like heat stable components being unaffected by the agent. 

D-2-Acetamido-2-deoxyhexosidase has been purified from an edible mushroom, Tremella fuciformis, to a single protein band (mol. wt. 1.25 x 10 by gel filtration) on disc gel electrophoresis. The enzyme (pH optimum 5.0, 0,19... 

A search for lysosomal hydrolases and related enzymes has been made in haemolysates from human and rabbit red cells. Apart from acid phosphatases, significant activities were found only for a-D-mannosidase, neutral o-D-glucosidase, and -D-2-acetamido-2-deoxyhexosidase. a-D-Mannosidase activity per cell in human red blood cells was 200-times lower than in white cells. The optimal pH was 5.5-6.0. Electrophoresis on cellulose acetate showed three bands. Haemolysates from four patients with mannosidosis were not deficient in a-D-mannosidase. Curves of pH activity and electrophoretic patterns were similar to those of controls. From its biochemical and genetic properties, it is concluded that red cell a-D-mannosidase differs from the lysosomal acid a-D-mannosidase. 

Dipeptide and aminoacyl derivatives of 4-nitrophenyl 2-amino-2-deoxy-P-o-glucopyranoside have been prepared, but only the iV-benzoyl- and N-benzyloxy-carbonyl-glycyl derivatives were cleaved at a significant rate by the p-D-2-acetamido-2-deoxyhexosidase from the mushroom Hohenbuecheliaserotina The synthesis of hexosaminyl derivatives of L-serine is mentioned in Chapter 3. 

The levels of P-D-2-acetamido-2-deoxyhexosidases A and B in the tissues and body fluids of normal individuals and Tay-Sachs patients have been measured by sensitive immunoassays specifically developed for this purpose. The results showed that normal tissues contain comparable amounts of both isoenzymes, whereas the tissues of Tay-Sachs patients contain neither the A isoenzyme nor material that carries A-specific antigenic determinants. The use of these assays in the diagnosis of Tay-Sachs disease was discussed. 

P-D-2-Acetamido-2-deoxyhexosidases A and B (each of mol. wt. 1.1 x 10 ) have been purified to homogeneity by affinity chromatography on immobilized concanavalin A and ion-exchange chromatography on diethyl(2-hydroxypropyl)-aminoethyl-Sephadex. Both enzymes contain neutral sugars (2.5 and 5.4%) and 2-acetamido-2-deoxy-D-glucose (2.5 and 3.4 %, respectively), but they do not appear to contain sialic acid. 

Characterization of the (3-D-2-acetamido-2-deoxyhexosidases C and S from the fibroblasts of controls and patients with Tay-Sachs disease did not provide any evidence for a structural relationship between P-D-2-acetamido-2-deoxyhexo-sidases A and C, so that a new interpretation of the results of man-rodent hybrids is favoured. ... 

The P-D-2-acetamido-2-deoxyhexosidase A from human kidneys is a heteropolymer composed of two immunologically distinct a and p subunits, whereas the corresponding B enzyme is a homopolymer composed of p subunits only. The physicochemical properties of the species obtained on dissociation of the enzymes with 4-hydroxymercuribenzoate have been studied, and attempts have been made to obtain hybrid species. It was concluded that the A form, (aff)3, dissociates into its subunits on reaction with the reagent and that the P subunits recombine to form the relatively stable B enzyme, (PP)3, whereas the a subunits recombine to form the dimer 2 and the polymer ag. 

Acetamido-2-deoxy-P-D-glucopyranosyl isothiocyanate irreversibly inhibited the P-D-2-acetamido-2-deoxyhexosidases from boar epididymis and human placenta, and dialysis did not restore the enzymic activity. 2-Acetamido-2-deoxy-D-glucose (a competitive inhibitor) protected the enzyme from inactivation, showing that the isothiocyanate binds at the active site of the enzyme. 

P-D-2-Acetamido-2-deoxyhexosidase from bull epididymis has been purified by affinity chromatography on a benzidine derivative of agarose to which monosaccharide lactones had been covalently attached. The use of 2-acetamido-2-deoxy-D-mannono-1,5-lactone is advantageous, and the enzyme fraction obtained could be separated into two bands, one of which was enzymically active, by electrophoresis on polyacrylamide gel. 

The B variant of the P-D-2-acetamido-2-deoxyhexosidase from pig epididymis has been separated into two isoenzymes (B and B ) for the first time. Like those... 

The pinocytosis by fibroblasts of )3-D-2-acetamido-2-deoxyhexosidase excreted by cultured fibroblasts from patients with mucolipidosis II disease is not enhanced by neuraminidase-catalysed removal of neuraminic acid residues from the j8-D-2-acetamido-2-deoxyhexosidase. ... 

The screening and prevention of Tay-Sachs disease, which involves a deficiency of j8-D-2-acetamido-2-deoxyhexosidase A, has been reviewed as part of the Progress in Clinical and Biological Research series. ... 

To examine the possibility in infantile Gm2 gangliosidosis (AB variant) of a mutant jS-D-2-acetamido-2-deoxyhexosidase A, well capable of hydrolysing the fluorogenic synthetic substrates, but unable to attack the relevant ganglio-side, the enzyme was isolated from patient tissue and characterized biochemically and immunologically in comparison with an enzyme preparation from normal tissue. The lack of differences between the two enzyme preparations indicated that the defect involved in the disease is not at the genetic level of production of either a or j8 chains of j3-D-2-acetamido-2-deoxyhexosidase A. 

Levels of lysosomal j8-D-2-acetamido-2-deoxyhexosidase have been determined in normal human hair roots and in hair roots obtained from a patient with mannosidosis. The significance of the results was discussed in relation to the levels of other glycoside hydrolases present, and to the detection of lysosomal storage disease. The f3-D-2-acetamido-2-deoxyhexosidase was found to be the most active glycoside hydrolase in normal hair roots. 

D-2-Acetamido-2-deoxyhexosidase isoenzymes A and B have been isolated from human kidney, in a homogeneous state as demonstrated by electrophoretic and enzymic criteria. The enzymes (Am s 0.8 mM for 4-nitrophenyl 2-acetamido-2-deoxy-j8-D-glucopyranoside, double pH optima for both, 4.S and 4.8) were stable for at least 18 months at —20 "C, pH 6.5. On sodium dodecyl sulphate-polyacrylamide gel electrophoresis isoenzyme A (mol. wt. 1.110 0.015 X 10 by gel filtration) dissociated into one subunit type (mol. wt. 6.8 X 10 ) and isoenzyme B (mol. wt. 1.140 0.016 x 10 ) into three subunits (mol. wts. 1.00 x 10 , 0.68 x 10 , and 0.37 x 10 ) and one protein band (mol. wt. 1.40 x 10 ). The effects of carboxymethylation on subunit phenomena and the activating/inactivating effects of metal ions were examined. 

Those proteins (mol. wts. 7.0—20 x 10 ) of human liver that cross-reacted with antibodies raised to apparently homogeneous j3-D-2-acetamido-2-deoxyhexosidases A and B were detected by immunodiffusion. The possible structure and functional relationships between the enzymes and the crossreacting proteins were discussed. 

An automated and reliable method has been described for the identification of heterozygous carriers of Tay-Sachs disease. The method was based on determination of j8-D-2-acetamido-2-deoxyhexosidase A activity in tears using 4-methylumbeIliferyl 2-acetamido-2-deoxy-j8-D-glucopyranoside as substrate. 

The specific activity and distribution of the isoenzymes of j8-D-2-acetamido-2-deoxyhexosidase have been studied in platelets, granulocytes, monocytes, and... 

A method described for the continuous kinetic measurement of serum j8-D-2-acetamido-2-deoxyhexosidase activity has been applied to detection of heterozygotes for Tay-Sachs gene. In contrast to single-point methods, a pH of 4.5, which is optimal for the enzyme activity on 4-methylumbelliferyl 2-acetamido-2-deoxy-jS-D-glucopyranoside, is maintained whilst the increase in fluorescence for the reaction product, 4-methylumbelliferone, is determined. Under the conditions described, the reaction followed zero-order kinetics, and activity was linearly related to serum dilution. 

The levels of j8-D-2-acetamido-deoxyglucosidase activity in skin fibroblasts from cases of cystic fibrosis and controls have been compared. In a study of I-cell disease (mucolipidosis II) a model has been presented for the structure of the carbohydrate recognition site of fibroblast-derived )3-D-2-acetamido-2-deoxyhexosidase that may extend to the other affected hydrolases and that is responsible for specific uptake of the enzyme by fibroblasts. ... 

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