4o8n

Publication Abstract from PubMed

Xylan debranching enzymes facilitate the complete hydrolysis of xylan and can be used to alter xylan chemistry. Herein, the GH62 family alpha-l-arabinofuranosidase from Streptomyces thermoviolaceus (SthAbf62A) was shown to have a half-life of 60 min at 60 degrees C, and ability to cleave alpha-1,3 l-arabinofuranose (l-Araf ) from singly-substituted xylopyranosyl (Xylp) backbone residues in wheat arabinoxylan; low activity towards arabinan as well as 4-nitrophenyl alpha-l-arabinofuranoside was also detected. After selectively removing alpha-1,3 l-Araf substituents from di-substituted Xylp residues present in wheat arabinoxylan, SthAbf62A could also cleave the remaining alpha-1,2 l-Araf substituents, confirming the ability of SthAbf62A to remove alpha-l-Araf residues that are (1-->2) and (1-->3) linked to mono-substituted beta-d-Xylp sugars. Three-dimensional structures of SthAbf62A and its complex with xylotetraose and l-arabinose confirmed a five-bladed beta-propeller fold and revealed a molecular Velcro in blade V between the beta1 and beta21 strands, a disulfide bond between Cys 27 and Cys 297, and a calcium ion coordinated in the central channel of the fold. The enzyme-arabinose complex structure further revealed a narrow and seemingly rigid l-arabinose binding pocket situated at the center of one side of the beta propeller, which stabilized the arabinofuranosyl substituent through several hydrogen-bonding and hydrophobic interactions. The predicted catalytic amino acids were oriented towards this binding pocket and the catalytic essentiality of Asp53 and Glu213 was confirmed by site-specific mutagenesis. Complex structures with xylotetraose revealed a shallow cleft for xylan backbone binding which is open at both ends and comprises multiple binding subsites above and flanking the l-arabinose binding pocket.

Biochemical and structural characterization of a thermostable family GH62 alpha-l-arabinofuranosidase from Streptomyces thermoviolaceus to elucidate the molecular basis for activity towards arabinoxylan.,Wang W, Mai-Gisondi G, Stogios PJ, Kaur A, Xu X, Cui H, Turunen O, Savchenko A, Master ER Appl Environ Microbiol. 2014 Jun 20. pii: AEM.00685-14. PMID:24951792^[1]

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