title: Substrate cleavage pattern, biophysical characterization and low-resolution structure of a novel hyperthermostable arabinanase from Thermotoga petrophila.
abstract: Arabinan is a plant structural polysaccharide degraded by two enzymes; alpha-l-arabinofuranosidase and endo-1,5-alpha-l-arabinanase. These enzymes are highly diversified in nature, however, little is known about their biochemical and biophysical properties. We have characterized a novel arabinanase (AbnA) isolated from Thermotoga petrophila with unique thermostable properties such as the insignificant decrease of residual activity after incubation up to 90 degrees C. We determined the AbnA mode of operation through capillary zone electrophoresis, which accumulates arabinotriose and arabinobiose as end products after hydrolysis of arabinan-containing polysaccharides. Spectroscopic analyses by Far-UV circular dichroism and intrinsic tryptophan fluorescence emission demonstrated that AbnA is folded and formed mainly by beta-sheet structural elements. In silico molecular modeling showed that the AbnA structure encompasses a five-bladed beta-propeller catalytic core juxtaposed by distorted up-and-down beta-barrel domain. The low-resolution structure determined by small angle X-ray scattering indicated that AbnA is monomeric in solution and its molecular shape is in full agreement with the model.
authors.affiliation: Laboratório Nacional de Ciência e Tecnologia do Bioetanol (CTBE), do Centro Nacional de Pesquisa em Energia e Materiais (CNPEM), Campinas, SP, Brazil. fabio.squina@bioetanol.org.br
authors.forename: Fabio M
authors.initials: FM
authors.lastname: Squina
authors.forename: Camila R
authors.initials: CR
authors.lastname: Santos
authors.forename: Daniela A
authors.initials: DA
authors.lastname: Ribeiro
authors.forename: Júnio
authors.initials: J
authors.lastname: Cota
authors.forename: Renata R
authors.initials: RR
authors.lastname: de Oliveira
authors.forename: Roberto
authors.initials: R
authors.lastname: Ruller
authors.forename: Andrew
authors.initials: A
authors.lastname: Mort
authors.forename: Mario T
authors.initials: MT
authors.lastname: Murakami
authors.forename: Rolf A
authors.initials: RA
authors.lastname: Prade
mesh_terms: D006026:Glycoside Hydrolases / Q000737:chemistry* / Q000235:genetics; D016965:Gram-Negative Anaerobic Straight, Curved, and Helical Rods / Q000201:enzymology*; D011487:Protein Conformation; D053838:Scattering, Small Angle; D013379:Substrate Specificity; D014961:X-Ray Diffraction
chemical_list: D006026:Glycoside Hydrolases; C019713:alpha-N-arabinofuranosidase