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Publication Abstract from PubMed

alpha-Galactosidase catalyzes the hydrolysis of a terminal alpha-galactose residue in galacto-oligosaccharides and has potential in various industrial applications and food processing. We determined the crystal structures of alpha-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 (beta/alpha)8 barrel domain, and a C-terminal domain. The domain organization is similar to that of the other family of 36 alpha-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 alpha-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 alpha-galactosidase family.

Crystal Structure of alpha-Galactosidase from Thermus thermophilus: Insight into Hexamer Assembly and Substrate Specificity.,Chen SC, Wu SP, Chang YY, Hwang TS, Lee TH, Hsu CH J Agric Food Chem. 2020 Jun 3;68(22):6161-6169. doi: 10.1021/acs.jafc.0c00871., Epub 2020 May 20. PMID:32390413^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.