Characterization of an Exo-β-1,3-D-galactanase from Streptomyces avermitilis NBRC14893 Acting on Arabinogalactan-Proteins
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A gene belonging to glycoside hydrolase family 43 (GH43) was isolated from <I>Streptomyces avermitilis</I> NBRC14893. The gene encodes a modular protein consisting of N-terminal GH43 module and a family 13 carbohydrate-binding module at the C-terminus. The gene corresponding to the GH43 module was expressed in <I>Escherichia coli</I>, and the gene product was characterized. The recombinant enzyme specifically hydrolyzed only β-1,3-linkage of two <small>D</small>-galactosyl residues at non-reducing ends of the substrates. The analysis of the hydrolysis products indicated that the enzyme produced galactose from β-1,3-<small>D</small>-galactan in an exo-acting manner. When the enzyme catalyze hydrolysis of the arabinogalactan-protein, the enzyme produced oligosaccharides together with galactose, suggesting that the enzyme is able to accommodate β-1,6-linked <small>D</small>-galactosyl side chains. These properties are the same as the other previously reported exo-β-1,3-<small>D</small>-galactanases. Therefore, we concluded the isolated gene certainly encodes an exo-β-1,3-<small>D</small>-galactanase. This is the first report of exo-β-1,3-<small>D</small>-galactanase from actinomycetes.
- Agricultural and Biological Chemistry
Agricultural and Biological Chemistry 70(11), 2745-2750, 2006-11-23
Japan Society for Bioscience, Biotechnology, and Agrochemistry