Fabry disease: biochemical, pathological and structural studies of the α-galactosidase A with E66Q amino acid substitution.
Recently, male subjects harboring the c.196G>C nucleotide change which leads to the E66Q enzyme having low α-galactosidase A (GLA) activity have been identified at an unexpectedly high frequency on Japanese and Korean screening for Fabry disease involving dry blood spots and plasma/serum samples. Individuals with the E66Q enzyme have been suspected to have the later-onset Fabry disease phenotype leading to renal and cardiac disease. However, there has been no convincing evidence for this. To determine whether c.196G>C (E66Q) is disease-causing or not, we performed biochemical, pathological and structural studies. It was predicted that the E66Q amino acid substitution causes a small conformational change on the molecular surface of GLA, which leads to instability of the enzyme protein. However, biochemical studies revealed that subjects harboring the E66Q enzyme exhibited relatively high residual enzyme activity in white blood cells, and that there was no accumulation of globotriaosylceramide in cultured fibroblasts or an increased level of plasma globotriaosylsphingosine in these subjects. An electron microscopic examination did not reveal any pathological changes specific to Fabry disease in biopsied skin tissues from a male subject with the E66Q enzyme. These results strongly suggest that the c.196G>C is not a pathogenic mutation but is a functional polymorphism.
Department of Analytical Biochemistry, Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose, Tokyo 204-8588, Japan.
Tadayasu
T
Togawa
Takahiro
T
Tsukimura
Takashi
T
Kodama
Toshie
T
Tanaka
Ikuo
I
Kawashima
Seiji
S
Saito
Kazuki
K
Ohno
Tomoko
T
Fukushige
Takuro
T
Kanekura
Atsushi
A
Satomura
Duk-Hee
DH
Kang
Beom Hee
BH
Lee
Han-Wook
HW
Yoo
Kent
K
Doi
Eisei
E
Noiri
Hitoshi
H
Sakuraba
D000368:Aged; D000369:Aged, 80 and over; D019943:Amino Acid Substitution; D044466:Asian People; D002478:Cells, Cultured; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D000795:Fabry Disease / Q000201:enzymology* / Q000235:genetics* / Q000473:pathology; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology; D006579:Heterozygote; D006801:Humans; D015151:Immunoblotting; D008297:Male; D008854:Microscopy, Electron; D008875:Middle Aged; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics*; D010641:Phenotype; D060888:Real-Time Polymerase Chain Reaction; D012867:Skin / Q000166:cytology / Q000201:enzymology; D014281:Trihexosylceramides / Q000097:blood; D000519:alpha-Galactosidase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
D014281:Trihexosylceramides; C018549:globotriaosylceramide; D000519:alpha-Galactosidase