Isolation and divalent-metal activation of a β-xylosidase, RUM630-BX

Autor: J. Rose Stoller, Kurt Wagschal, Jay D. Braker, Charles C. Lee, Douglas B. Jordan
Rok vydání: 2016
Předmět:
Zdroj: Enzyme and Microbial Technology. 82:158-163
ISSN: 0141-0229
DOI: 10.1016/j.enzmictec.2015.10.001
Popis: The gene encoding RUM630-BX, a β-xylosidase/arabinofuranosidase, was identified from activity-based screening of a cow rumen metagenomic library. The recombinant enzyme is activated as much as 14-fold (kcat) by divalent metals Mg(2+), Mn(2+) and Co(2+) but not by Ca(2+), Ni(2+), and Zn(2+). Activation of RUM630-BX by Mg(2+) (t0.5 144 s) is slowed two-fold by prior incubation with substrate, consistent with the X-ray structure of closely related xylosidase RS223-BX that shows the divalent-metal activator is at the back of the active-site pocket so that bound substrate could block its entrance. The enzyme is considerably more active on natural substrates than artificial substrates, with activity (kcat/Km) of 299 s(-1) mM(-1) on xylotetraose being the highest reported.
Databáze: OpenAIRE