Crystal structure of rice alpha-galactosidase complexed with D-galactose.
alpha-Galactosidases catalyze the hydrolysis of alpha-1,6-linked galactosyl residues from galacto-oligosaccharides and polymeric galacto-(gluco)mannans. The crystal structure of rice alpha-galactosidase has been determined at 1.5A resolution using the multiple isomorphous replacement method. The structure consisted of a catalytic domain and a C-terminal domain and was essentially the same as that of alpha-N-acetylgalactosaminidase, which is the same member of glycosyl hydrolase family 27. The catalytic domain had a (beta/alpha)8-barrel structure, and the C-terminal domain was made up of eight beta-strands containing a Greek key motif. The structure was solved as a complex with d-galactose, providing a mode of substrate binding in detail. The d-galactose molecule was found bound in the active site pocket on the C-terminal side of the central beta-barrel of the catalytic domain. The d-galactose molecule consisted of a mixture of two anomers present in a ratio equal to their natural abundance. Structural comparisons of rice alpha-galactosidase with chicken alpha-N-acetylgalactosaminidase provided further understanding of the substrate recognition mechanism in these enzymes.
Fujimoto
Zui
Z
Department of Biochemistry, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8602, Japan.
Kaneko
Satoshi
S
Momma
Mitsuru
M
Kobayashi
Hideyuki
H
Mizuno
Hiroshi
H
D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D005690:Galactose / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D012275:Oryza / Q000201:enzymology*; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D000519:alpha-Galactosidase / Q000737:chemistry* / Q000378:metabolism
D000519:alpha-Galactosidase; D005690:Galactose