Abstract
Abstract The gene encoding glycosyl hydrolase family 115 α-glucuronidase from Scheffersomyces stipitis (ssagu115) was cloned and expressed in Pichia pastoris strain X33. The recombinant enzyme was purified to homogeneity by Ni-chelation affinity chromatography. The apparent molecular weight of the secreted recombinant enzyme was about 150 kDa as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The recombinant α-glucuronidase was able to remove 4-O-methylglucuronic acid groups from several polymeric xylans (beech, birch, and oat spelt xylan) as well as xylooligosaccharides (aldotetraouronic acid and aldopentaouronic acid). The enzyme was more active towards xylooligosaccharides than xylans. Substrate inhibition was observed with aldouronic acids at concentrations above 23 mM. The Km values of the enzyme towards aldotetraouronic and aldopentaouronic acids were 8.2 mM (5 mg/mL) and 9 mM (6.5 mg/mL), respectively. For beech and birch xylan, the Km values were 9.5 mg/mL and 35 mg/mL, re...
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