Purification of Xyloglucan Hydrolase/Endotransferase from Cell Walls of Azuki Bean Epicotyls |
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Authors: | Tabuchi, Akira Kamisaka, Seiichiro Hoson, Takayuki |
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Affiliation: | Department of Biology, Faculty of Science, Osaka City University Sumiyoshi-ku, Osaka, 558 Japan |
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Abstract: | An enzyme involved in the breakdown of xyloglucans was purifiedfrom an extract of cell walls of azuki bean epicotyls obtainedwith 1 M NaCl and purified by column chromatography on severaldifferent resins. The purified enzyme gave a single band ofa protein with a molecular mass of about 32 kDa after SDS-PAGE.The enzyme hydrolyzed the xyloglucans of high molecular massfrom azuki cell walls to yield fragments of about 50 kDa withoutproduction of any oligo- or monosaccharides. Moreover, the enzymehad hardly any effect on xyloglucans of less than 60 kDa. Theenzyme also hydrolyzed xyloglucans from tamarind, but it didnot react with cellulose derivatives. In the presence of pyridylamino-labeledxyloglucan oligosac-charides as acceptor substrates, the enzymecatalyzed the transfer of 50-kDa products to the oligosaccharides.The Km value of the enzyme for xyloglucans of 540 kDa was similarin the presence and in the absence of xyloglucan oligosaccharidesas acceptors: 1.0 mg ml1. These results suggest thatthe enzyme was an endotransferase but had unusual acceptor specificity,preferring smaller acceptors such as water. (Received September 9, 1996; Accepted March 16, 1997) |
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