| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2006: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2005: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Research Abstract |
Arabinogalactan-proteins (AGPs) constitute an abundant class of highly glycosylated hydroxyproline-rich glycoproteins found in the extracellular matrix associated with plasma membrane and cell wall of higher plants. AGPs are differentially expressed during plant development and have been implicated in many fundamental phenomena such as cell expansion, recognition, differentiation, programmed cell death, sexual plant reproduction and embryogenesis. In spite of significance of AGPs, only limited research relating AGPs degrading enzymes were performed. Therefore, for the first time, we cloned exo-1,3-galactanase from Phanerochaete chrysosporium, Clostridium thermocellum, Streptomyces a vermitilis.
The all of the recombinant enzymes specifically hydrolyzed only β-1,3-linkage of two D-galactosyl residues at non-reducing ends of the substrates. When the enzyme catalyze hydrolysis of the arabinogalactan-protein, the enzyme produced oligosaccharides together with galactose, suggesting that the enzyme is able to accommodate a β-1,6-linked D-galactosyl side chain.
The C-terminal carbohydrate binding module (CBM) of exo-1,3-galactanase from P.chrysosporium (CBM35) specifically bound to oligosaccharides containing at least two β-1,3-linked galactosyl residues. In contrast, CBM family 13 module of exo-1,3-galactanase from C.thermocellum showed broad substrate specificity for galactose containing oligosaccharides.
To understand the structure-function relationships of exo-1,3-galactanases, crystals of the enzyme from P.chrysosporium was prepared. The obtained crystal showed diffraction beyond 2.2 A resolution but the structure could not determined.
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