The Mode of Synthesis of Levan by Bacillus subtilis Levansucrase

概要

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The transfer action of Bacillus subtilis levansucrase was further studied and the following results were obtained: the levan synthesized on raffinose by the enzyme contained one mole of galactosylglucose per mole as one of the two terminal glycosyl moieties. The enzyme synthesized levanbiose in a mixture of fructose and 14C-fructose-containing sucrose and the ether linkage formed was between the C2 of labelled fructose and the C6 of non-labelled fructose. The transfer of fructosyl residues by the enzyme was suppressed as the ionic strength of the reaction mixture increased. This suppression effect of ionic strength was severe in the synthesis of high molecular weight levan. The hydrolysis of levan by the levansucrase was also suppressed by the increase of ionic strength, but this effect occurred with almost the same degree in the hydrolysis of both low and high molecular weight levans. On the basis of these results, the extending direction of the levan molecule and the exclusive synthesis of low molecular weight levan in the presence of high ionic strength are discussed.
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