Structural and biochemical studies on Pompe disease and a "pseudodeficiency of acid alpha-glucosidase".
We constructed structural models of the catalytic domain and the surrounding region of human wild-type acid alpha-glucosidase and the enzyme with amino acid substitutions by means of homology modeling, and examined whether the amino acid replacements caused structural and biochemical changes in the enzyme proteins. Missense mutations including p.R600C, p.S619R and p.R437C are predicted to cause apparent structural changes. Nonsense mutation of p.C103X terminates the translation of acid alpha-glucosidase halfway through its biosynthesis and is deduced not to allow formation of the active site pocket. The mutant proteins resulting from these missense and nonsense mutations found in patients with Pompe disease are predictably unstable and degraded quickly in cells. The structural change caused by p.G576S is predicted to be small, and cells from a subject homozygous for this amino acid substitution exhibited 15 and 11% of the normal enzyme activity levels for an artificial substrate and glycogen, respectively, and corresponding amounts of the enzyme protein on Western blotting. No accumulation of glycogen was found in organs including skeletal muscle in the subject, and thus the residual enzyme activity could protect cells from glycogen storage. On the other hand, p.E689K, which is known as a neutral polymorphism, little affected the three-dimensional structure of acid alpha-glucosidase. Structural study on a mutant acid alpha-glucosidase in silico combined with biochemical investigation is useful for understanding the molecular pathology of Pompe disease.
Tajima
Youichi
Y
Department of Clinical Genetics, The Tokyo Metropolitan Institute of Medical Science, Tokyo Metropolitan Organization for Medical Research, Tokyo, Japan.
Matsuzawa
Fumiko
F
Department of Clinical Genetics, The Tokyo Metropolitan Institute of Medical Science, Tokyo Metropolitan Organization for Medical Research, Tokyo, Japan.
Aikawa
Sei-Ichi
SI
Department of Clinical Genetics, The Tokyo Metropolitan Institute of Medical Science, Tokyo Metropolitan Organization for Medical Research, Tokyo, Japan.
Okumiya
Toshika
T
Department of Analytical Biochemistry, School of Health Sciences, Kumamoto University, Kumamoto, Japan.
Yoshimizu
Michiru
M
Department of Clinical Genetics, The Tokyo Metropolitan Institute of Medical Science, Tokyo Metropolitan Organization for Medical Research, Tokyo, Japan.|Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Noda, Japan.
Tsukimura
Takahiro
T
Department of Clinical Genetics, The Tokyo Metropolitan Institute of Medical Science, Tokyo Metropolitan Organization for Medical Research, Tokyo, Japan.|Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Noda, Japan.
Ikekita
Masahiko
M
Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Noda, Japan.
Tsujino
Seiichi
S
Department of Peripheral Nervous System Research, National Institute of Neuroscience, NCNP, Kodaira, Japan.
Tsuji
Akihiko
A
Department of Biological Science and Technology, Faculty of Engineering, University of Tokushima, Tokushima, Japan.
Edmunds
Tim
T
Genzyme Corporation, Framingham, MA, USA.
Sakuraba
Hitoshi
H
Department of Clinical Genetics, The Tokyo Metropolitan Institute of Medical Science, Tokyo Metropolitan Organization for Medical Research, Tokyo, Japan. sakuraba@my-pharm.ac.jp.|Department of Analytical Biochemistry, Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose, Tokyo, 204-8588, Japan. sakuraba@my-pharm.ac.jp.
D000595:Amino Acid Sequence; D015153:Blotting, Western; D002478:Cells, Cultured; D006009:Glycogen Storage Disease Type II / Q000201:enzymology / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D000520:alpha-Glucosidases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism