TAILIEUCHUNG - Báo cáo khoa học: Aglycone specificity of Escherichia coli a-xylosidase investigated by transxylosylation

The specificity of the aglycone-binding site ofEscherichia colia-xylosidase (YicI), which belongs to glycoside hydrolase family 31, was characterized by examining the enzyme’s transxylosylation-catalyzing property. Acceptor specificity and regioselectivity were investigated using various sugars as acceptor substrates anda-xylosyl fluoride as the donor substrate. | ễFEBS Journal Aglycone specificity of Escherichia coli a-xylosidase investigated by transxylosylation Min-Sun Kang1 Masayuki Okuyama1 Katsuro Yaoi2 Yasushi Mitsuishi2 Young-Min Kim3 Haruhide Mori1 Doman Kim3 and Atsuo Kimura1 1 Division of Applied Bioscience Hokkaido University Sapporo Japan 2 Institute for BiologicalResources and Functions Ibaraki Japan 3 Laboratory of FunctionalCarbohydrate Enzyme and MicrobialGenomics Chonnam NationalUniversity Gwang-Ju South Korea Keywords acceptor specificity aglycone-binding site Escherichia coli a-xylosidase intestinal a-glucosidase inhibitor novel xylooligosaccharide Correspondence A. Kimura or M. Okuyama Division of Applied Bioscience Research Faculty of Agriculture Hokkaido University Kita-9 Nishi-9 Kita-ku Sapporo 060-8589 Japan Fax 81 11 706 2808 Tel 81 11 706 2808 E-mail kimura@ okuyama@ Received 17 July 2007 revised 11 September 2007 accepted 5 October 2007 doi The specificity of the aglycone-binding site of Escherichia coli a-xylosidase YicI which belongs to glycoside hydrolase family 31 was characterized by examining the enzyme s transxylosylation-catalyzing property. Acceptor specificity and regioselectivity were investigated using various sugars as acceptor substrates and a-xylosyl fluoride as the donor substrate. Comparison of the rate of formation of the glycosyl-enzyme intermediate and the transfer product yield using various acceptor substrates showed that glucose is the best complementary acceptor at the aglycone-binding site. YicI preferred aldopyranosyl sugars with an equatorial 4-OH as the acceptor substrate such as glucose mannose and allose resulting in transfer products. This observation suggests that 4-OH in the acceptor sugar ring made an essential contribution to transxylosylation catalysis. Fructose was also acceptable in the aglycone-binding site producing two regioisomer transfer products. The percentage yields of .

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