学術雑誌論文 Functional reassignment of Cellvibrio vulgaris EpiA to cellobiose 2-epimerase and an evaluation of the biochemical functions of the 4-O-beta-d-mannosyl-d-glucose phosphorylase-like protein, UnkA

Saburi, Wataru  ,  Tanaka, Yuka  ,  Muto, Hirohiko  ,  Inoue, Sota  ,  Odaka, Rei  ,  Nishimoto, Mamoru  ,  Kitaoka, Motomitsu  ,  Mori, Haruhide

79 ( 6 )  , pp.969 - 977 , 2015-06-04 , Taylor & Francis
ISSN:0916-8451
内容記述
The aerobic soil bacterium Cellvibrio vulgaris has a beta-mannan-degradation gene cluster, including unkA, epiA, man5A, and aga27A. Among these genes, epiA has been assigned to encode an epimerase for converting d-mannose to d-glucose, even though the amino acid sequence of EpiA is similar to that of cellobiose 2-epimerases (CEs). UnkA, whose function currently remains unknown, shows a high sequence identity to 4-O-beta-d-mannosyl-d-glucose phosphorylase. In this study, we have investigated CE activity of EpiA and the general characteristics of UnkA using recombinant proteins from Escherichia coli. Recombinant EpiA catalyzed the epimerization of the 2-OH group of sugar residue at the reducing end of cellobiose, lactose, and beta-(1 -> 4)-mannobiose in a similar manner to other CEs. Furthermore, the reaction efficiency of EpiA for beta-(1 -> 4)-mannobiose was 5.5x10(4)-fold higher than it was for d-mannose. Recombinant UnkA phosphorolyzed beta-d-mannosyl-(1 -> 4)-d-glucose and specifically utilized d-glucose as an acceptor in the reverse reaction, which indicated that UnkA is a typical 4-O-beta-d-mannosyl-d-glucose phosphorylase.
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http://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/62061/1/70427%ef%bc%88mori%ef%bc%89pdf.pdf

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