Detection and properties of an acid -galactosidase (ceramidetrihexosidase) in normal human urine

Enzyme Replacement Therapy for FABRY Disease: Possible Strategies to Improve Its Efficacy

Enzyme replacement therapy is the only therapeutic option for Fabry patients with completely absent AGAL activity. However, the treatment has side effects, is costly, and requires conspicuous amounts of recombinant human protein (rh-AGAL). Thus, its optimization would benefit patients and welfare/health services (i.e., society at large). In this brief report, we describe preliminary results paving the way for two possible approaches: i. the combination of enzyme replacement therapy with pharmacological chaperones; and ii. the identification of AGAL interactors as possible therapeutic targets on which to act. We first showed that galactose, a low-affinity pharmacological chaperone, can prolong AGAL half-life in patient-derived cells treated with rh-AGAL. Then, we analyzed the interactomes of intracellular AGAL on patient-derived AGAL-defective fibroblasts treated with the two rh-AGALs approved for therapeutic purposes and compared the obtained interactomes to the one associated with endogenously produced AGAL (data available as PXD039168 on ProteomeXchange). Common interactors were aggregated and screened for sensitivity to known drugs. Such an interactor-drug list represents a starting point to deeply screen approved drugs and identify those that can affect (positively or negatively) enzyme replacement therapy.

Comparative studies on six blood serum glycosidases from several mammalian species

1. Peripheral blood serum alpha-D-galactosidase, beta-D-galactosidase, beta-D-glucosidase, alpha-D-mannosidase, beta-D-xylosidase and beta-D-glucuronidase have been studied with a comparative point of view from several mammalian species: Bos taurus L. (bull), Capra hircus L. (goat), Sus scropha var. domestica L. (pig) and man. 2. Fluorimetric and spectrophotometric procedures were used for determination of enzyme activities and pH optima. 3. Glycosidase activity was generally higher with fluorescent substrates than with chromogenic substrates. 4. alpha-D-mannosidase was the most active with both fluorescent and chromogenic substrates. 5. All the studied enzymes had the same pH optimum (4.0) when the chromogenic substrates were used. 6. pH optima of these glycosidases ranged from 3.0 to 5.5 when the fluorescent substrates were used.

Properties of immobilized fig alpha-galactosidase and effect on ceramide-3 content of plasma from patients with Fabry's disease

The possibility of lowering the level of ceramide-3 (galactosyl-alpha(1 leads to 4)-galactosyl-beta(1 leads to 4)-glucosyl-beta(1 leads to 1)-ceramide) in the plasma of patients with Fabry's disease was investigated. An immobilized alpha-galactosidase (alpha-D-galactoside galactohydrolase, EC 3.2.1.22) was prepared by coupling purified fig alpha-galactosidase to Sepharose 4B. The pH optimum for the hydrolysis of the artificial substrate p-nitro-phenyl-alpha-D-galactopyranoside was shifted by approx. 0.5--1.0 pH unit to higher pH values upon coupling of the enzyme to Sepharose 4B. The immobilized enzyme was more stable than the native enzyme to incubation at 60 degrees C. The immobilized enzyme was able to hydrolyse ceramide-3 either at pH 4.5 or at pH 7.4 in an artificial system in which sodium taurocholate was used to solubilize the substrate. In contrast, when the immobilized enzyme was incubated with normal plasma or plasma from a patient with Fabry's disease, in which elevated levels of ceramide-3 occur, no hydrolysis of the glycosphingo-lipid could be detected. The results suggest that lowering of level of ceramide-3 in plasma from patients with Fabry's disease by enzymic means is not feasible.

Enzymological properties and immunological characterization of alpha-galactosidase isoenzymes from normal and Fabry human liver

1. A method is described for the rapid isolation of alpha-galactosidases A and B (alpha-D-galactoside galactohydrolase, EC 3.2.1.22) from normal human liver. 2. When the same method is applied to Fabry liver, most of the alpha-galactosidase activity is recovered in the fraction corresponding to normal alpha-galactosidase B. In agreement with Romeo, G., D'Urso, M., Pisacane, A., Blum, E., De Falco, A. and Ruffilli, A. (1975) Biochem. Genet. 13, 615-628) [18], a small amount of alpha-galactosidase activity is found in the fraction corresponding to normal alpha-galactosidase A. 3. The kinetic properties of the B-like activity from Fabry liver are similar to those of normal alpha-galactosidase B. In agreement with Romeo et al. [18], it was found that the kinetic properties of the A-like activity from Fabry liver are similar to those of normal alpha-galactosidase A. 4. Using antisera raised against normal alpha-galactosidase A and normal alpha-galactosidase B, it is shown that the normal alpha-galactosidase isoenzymes are immunologically distinct and that the B-like activity from Fabry liver is immunologically related to normal alpha-galactosidase B. Furthermore, the A-like activity from Fabry liver is immunologically related to normal alpha-galactosidase B and not to normal alpha-galactosidase A. 5. Normal alpha-galactosidase B is converted into an A-like form during storage. 6. It is concluded that the B-like alpha-galactosidase in Fabry tissues is identical to normal alpha-galactosidase B, and that the small amount of A-like activity found in Fabry material is due to a modified form of alpha-galactosidase B.

Characterization of alpha-galactosidase isoenzymes in normal and Fabry human-Chinese Hamster somatic cell hybrids

The alpha-galactosidases in normal man-Chinese hamster somatic cell hybrids were investigation with antibodies specific for human alpha-galactosidase A and antibodies specific for Chinese hamster alpha-galactosidase. It was found that an isoenzyme in hybrid cells, which has an electrophoretic mobility between that of human alpha-galactosidase A and Chinese hamster alpha-galactosidase, contains immunologic determinants of both human and Chinese hamster origin, suggesting that it is a heteropolymeric molecule. Moreover, the locus for human alpha-galactosidase, which was found to be X-linked, is the locus coding for alpha-galactosidase A. Hybrids isolated after fusion of Chinese hamster cells with cells of a patient with Fabry's disease did not express human alpha-galactosidase A or the heteropolymeric molecule even in the presence of the active human X chromosome, indicating that the deficiency of alpha-galactosidase A in Fabry's disease is probably due to a mutation in a structural gene resulting in the inability to form immunologically detectable and functionally active molecules of alpha-galactosidase A.

Human leucocyte alpha-L-fucosidase

1. Human alpha-L-fucosidase (EC 3.2.1.51) was studied from leucocytes, urine and serum. 2. The leucocyte and urine enzymes are similar in many properties (KM, pH optimum, electrophoretic pattern, heat stability). 3. The serum alpha-L-fucosidase differs from the leucocyte and 4rine enzyme wit,respect to: electrophoretic pattern, pH optimum and heat stapility. 4. The molecular weight of leucocyte alpha-L-fucosidase was determined to be 80 000 +/- 5000. 5. Cu2+, Hg2+ and PCMB are strong inhibitors of leucocyte alpha-L-fucosidase. This inhibition could be completely reversed by beta-mercaptoethanol, indicating that thiol groups are essential for catalytic activity.

Fabry disease: diagnosis by alpha-galactosidase activities in tears

The enzymatic diagnosis of hemizygotes with Fabry disease and heterozygous carriers was accomplished by the fluorometric determination of alpha-galactosidase activities in tears. Two components of total alpha-galactosidase activity were differentiated by their relative thermostabilities and by chromatography on DEAE-cellulose. The major component, alpha-galactosidase A, was thermolabile and represented approximately 90% of total activity; the remaining activity was thermostable, eluted at a slightly higher salt concentration and was designated alpha-galactosidase B. A single, symmetric pH optimum was observed for total alpha-galactosidase activities from heterozygotes and normal individuals, whereas the total activity from hemizgotes, which was about 10% of that in normal controls, had a broad pH profile, identical to those for alpha-galactosidase B activities from all individuals studied. The apparent Km values for total activities were 3.2, 4.0, and greater than 13 mM for normal individuals, heterozygotes, and hemizygotes, respectively. In contrast, apparent Km values for alpha-galactosidase B activities were greater than 13 mM for all individuals, further suggesteng that the residual activity in hemizygotes with Fabry disease represented the alpha-galactosidase B component. of the potential inhibitors studied, alpha-D-melibiose was found to competitively inhibit total alpha-galactosidase activity (Ki approximately 10 mM). These studies demonstrate that tears provide an easily obtainable source of freshly secreted enzyme for the diagnosis of hemizygotes and heterozygotes with Fabry disease and suggest that tears may be useful for the diagnosis of other inborn errors of metabolism.

Properties of the residual alpha-galactosidase activity in the tissues of a Fabry hemizygote

The properties of the residual alpha-galactosidase activity in kidney, liver, spleen, fibroblasts and urine of a Fabry hemizygote have been studied using p-nitrophenyl-alpha-galactoside and 4-methylumbelliferyl-alpha-galactoside as substrates. In addition, alpha-galactosidase activity in urine has been determined with ceramidetrihexoside as substrate. The residual alpha-galactosidase activity of Fabry, measured with artificial substrate, is stimulated (6-35%) by myo-inositol and only slightly inhibited by melibiose (7-17%) in all the materials used. In contrast, the alpha-galactosidase of normal tissues and urine is inhibited (36-48%) by myo-inositol and inhibited to a much greater extent (40-50%) by melibiose. The KM for artificial substrate of the residual activity of Fabry is higher than that of the alpha-galactosidase in normal kidney, liver, spleen, fibroblasts and urine. The residual activity of Fabry is generally more stable to heating than the activity in the normal materials, although exceptions were noted. When these properties are compared with those of the alpha-galactosidase isoenzymes in normal tissues and body fluids, the residual activity of Fabry material seems to be very similar to the minor component of normal tissue (alpha-galactosidase B). Moreover, the pH optimum curve of this minor component and of the Fabry alpha-galactosidase in urine are similar, whereas the major isoenzyme (alpha-galactosidase A) shows a curve much more like that of normal urine. The findings with ceramidetrihexoside as substrate indicate a possible discrepancy. Alpha-Galactosidase A hydrolyses ceramidetrihexoside, Fabry urine preparation does not. However, alpha-galactosidase B of normal urine shows a slight but definite ceramidetrihexosidase activity. No contamination of the B preparation with alpha-galactosidase A could be detected. The minimum hypothesis, supported by most of the experimental evidence, is that the residual activity of Fabry and normal alpha-galactosidase B are identical.

Characterization of human alpha-galactosidase A and B before and after neuraminidase treatment

It has been previously reported that following neuraminidase treatment alpha-galactosidase A is converted into the B form, as revealed by electrophoresis. By a variety of techniques such as isoelectrofocusing, DEAE-chromatography and by enzyme kinetic parameters, no conversion of alpha-galactosidase A into B, or the reverse, could be detected after neuraminidase treatment. Only an apparent transformation of alpha-galactosidase A into B was revealed by Cellogel electrophoresis. In addition, a discrepancy was noticed between the pattern of electrophoretic migration on starch gel and Cellogel and the net electrical charges of the two alpha-galactosidases as deduced by isoelectrofocusing and DEAE-cellulose. Neuraminidase treatment did not affect the activity of alpha-galactosidase A towards the natural substrate, ceramidetrihexoside, but the activity of alpha-galactosidase B decreased by about 30% under the same conditions. The two forms of alpha-galactosidases A and B used in this study were extensively purified by classical procedures.