Crystal Structure of α-Galactosidase from Thermus thermophilus: Insight into Hexamer Assembly and Substrate Specificity
Journal
Journal of Agricultural and Food Chemistry
Journal Volume
68
Journal Volume
68
Journal Issue
22
Journal Issue
22
Pages
6161
Start Page
6161
End Page
6169
ISSN
00218561
Date Issued
2020-06-03
Author(s)
Abstract
α-Galactosidase catalyzes the hydrolysis of a terminal α-galactose residue in galacto-oligosaccharides and has potential in various industrial applications and food processing. We determined the crystal structures of α-galactosidase from the thermophilic microorganism Thermus thermophilus (TtGalA) and its complexes with pNPGal and stachyose. The monomer folds into an N-terminal domain, a catalytic (β/α)8 barrel domain, and a C-terminal domain. The domain organization is similar to that of the other family of 36 α-galactosidases, but TtGalA presents a cagelike hexamer. Structural analysis shows that oligomerization may be a key factor for the thermal adaption of TtGalA. The structure of TtGalA complexed with stachyose reveals only the existence of one −1 subsite and one +1 subsite in the active site. Structural comparison of the stachyose-bound complexes of TtGalA and GsAgaA, a tetrameric enzyme with four subsites, suggests evolutionary divergence of substrate specificity within the GH36 family of α-galactosidases. To the best of our knowledge, the crystal structure of TtGalA is the first report of a quaternary structure as a hexameric assembly in the α-galactosidase family.
Subjects
hexamer assembly
stachyose
substrate specificity
thermostable
α-galactosidase
Publisher
American Chemical Society
Type
journal article