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Properties of Multiple Molecular Forms of alpha-Galactosidase and alpha-N Acetylgalactosaminidase from Normal and Fabry Leukocytes

1979; Wiley; Volume: 100; Issue: 2 Linguagem: Inglês

10.1111/j.1432-1033.1979.tb04180.x

1432-1033

Robert Salvayre, Arlette Maret, Anne Nègre, L Douste-Blazy,

Glycosylation and Glycoproteins Research

1 In normal human leukocytes three forms of methylumbelliferyl α-galactosidase (EC 3.2.1.22) are separated using preparative electrofocusing: form I (pI 5.00) and form II (pI 4.5) which are known in other tissues as α-galactosidase A and α-galactosidase B respectively, and a new major form that we name form IV (pI 3.95) which is characteristic of leukocytes. 2 In normal human leukocytes only one molecular form of p-nitrophenyl α-N-acetylgalactos-aminidase corresponding to the form II of methylumbelliferyl α-galactosidase (or α-galactosidase B) is present. 3 In leukocytes from patients with Fabry disease the deficient activity corresponds to forms I and IV, whereas the residual activity corresponds to form II. This single residual form seems to be identical to the normal p-nitrophenyl α-N-acetylgalactosaminidase. 4 In leukocytes the molecular forms of methylumbelliferyl α-galactosidase and p-nitrophenyl α-N-acetylgalactosaminidase from normal subjects and patients with Fabry disease can be divided into two groups on the basis of their enzymatic and genetic properties. One group is made of form I (isoenzyme A) and of the new major form IV: heat-labile, with close Km values for MeUmb-Gal (Km I = 2.1 × 10−3 M and Km IV = 1.9 × 10−3 M), inhibited by α-galactosides and mesoinositol and inactive in Fabry disease (coded by the same X-linked gene). The other group only concerns methylumbelliferyl α-galactosidase form II (isoenzyme B), or α-N-acetylgalactosaminidase. This form II from normal subjects has the same properties as the residual one from Fabry disease: heat-stable, close Km values for MeUmb-Gal (Km II = 5.1 × 10−3 M and KmF = 5.5 × 10−3 M) and for Nph-GalNAc (Km normal = 1.7 × 10−3 M and Km Fabry = 2.0 × 10−3 M), inhibited by α-galactosides and by α-N-acetylgalactosaminides. This form is coded by a gene different from the X-linked gene.