Fabry Disease: Characterization of α-Galactoslidase A Double Mutations and the D313Y Plasma Enzyme Pseudodeficiency Allele

Makiko Yasuda, Junaid Shabbeer, Stacy D. Benson, Irene Maire, Roger M. Burnett, Robert J. Desnick

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132 Scopus citations


Fabry disease, an X-linked inborn error of glycosphingolipid catabolism, results from mutations in the gene encoding the lysosomal exoglycohydrolase, α-galactosidase A (α-Gal A; GLA). In two unrelated classically affected males, two α-Gal A missense mutations were identified: R112C + D313Y (c.334C > T + c.937G > T) and C172G + D313Y (c.514T > G + c.937G > T). The D313Y lesion was previously identified in classically affected males as the single mutation [Eng et al., 1993] or in cis with another missense mutation, D313Y + G411D (c.937G > T + c.1232G > A) [Guffon et al., 1998]. To determine whether the D313Y mutation was a deleterious mutation or a coding region sequence variant, the frequency of D313Y in normal X-chromosomes, as well as its enzymatic activity and subcellular localization in COS-7 cells was determined. D313Y occurred in 0.45% of 883 normal X-chromosomes, while the R112C, C172G, and G411D missense mutations were not detected in over 500 normal X-chromosomes. Expression of D313Y in COS-7 cells resulted in ∼ 60% of wild-type enzymatic activity and showed lysosomal localization, while R112C, C172G, G411D, and the double-mutated constructs had markedly reduced or no detectable activity and were all retained in the endoplasmic reticulum. The expressed D313Y enzyme was stable at lysosomal pH (pH 4.6), while at neutral pH (pH 7.4), it had decreased activity. A molecular homology model of human α-Gal A, based on the X-ray crystal structure of chicken α-galactosidase B (α-Gal B; α-N-acetylgalactosaminidase) was generated [Garman et al., 2002], which provided evidence that D313Y did not markedly disrupt the α-Gal A enzyme structure. Thus, D313Y is a rare exonic variant with about 60% of wild-type activity in vitro and reduced activity at neutral pH, resulting in low plasma α-Gal A activity.

Original languageEnglish
Pages (from-to)486-492
Number of pages7
JournalHuman Mutation
Issue number6
StatePublished - 2003


  • Fabry disease
  • GLA
  • Lysosomal storage disease
  • Mutation analysis
  • Pseudodeficiency
  • Structural homology model


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