A carboxy-terminal truncation of human alpha-galactosidase A in a heterozygous female with Fabry disease and modification of the enzymatic activity by the carboxy-terminal domain. Increased, reduced, or absent enzyme activity depending on number of amino acid residues deleted.
Fabry disease is an X-linked disorder of glycosphingolipid metabolism caused by a deficiency of alpha-galactosidase A (alpha-Gal A). We identified a novel mutation of alpha-Gal A gene in a family with Fabry disease, which converted a tyrosine at codon 365 to a stop and resulted in a truncation of the carboxy (C) terminus by 65 amino acid (AA) residues. In a heterozygote of this family, although the mutant and normal alleles were equally transcribed in cultured fibroblasts, lymphocyte alpha-Gal A activity was approximately 30% of the normal control and severe clinical symptoms were apparent. COS-1 cells transfected with this mutant cDNA showed a complete loss of its enzymatic activity. Furthermore, those cotransfected with mutant and wildtype cDNAs showed a lower alpha-Gal A activity than those with wild type alone (approximately 30% of wild type alone), which suggested the dominant negative effect of this mutation and implied the importance of the C terminus for its activity. Thus, we generated mutant cDNAs with various deletion of the C terminus, and analyzed. Unexpectedly, alpha-Gal A activity was enhanced by up to sixfold compared with wild-type when from 2 to 10 AA residues were deleted. In contrast, deletion of 12 or more AA acid residues resulted in a complete loss of enzyme activity. Our data suggest that the C-terminal region of alpha-Gal A plays an important role in the regulation of its enzyme activity.
Miyamura
N
N
Department of Metabolic Medicine, Kumamoto University School of Medicine, Japan.
Araki
E
E
Matsuda
K
K
Yoshimura
R
R
Furukawa
N
N
Tsuruzoe
K
K
Shirotani
T
T
Kishikawa
H
H
Yamaguchi
K
K
Shichiri
M
M
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D000795:Fabry Disease / Q000235:genetics* / Q000628:therapy; D005260:Female; D006579:Heterozygote; D006801:Humans; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation; D010375:Pedigree; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000737:chemistry; D013329:Structure-Activity Relationship; D014960:X Chromosome; D000519:alpha-Galactosidase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
D012333:RNA, Messenger; D000519:alpha-Galactosidase