Studies on Dextransucrase. I. Formation of Riboflavinylglucoside in Destran-producing Cultures of Leuconostoc Mesenteroides.

The dextran produced by this enzymic synthesis has been ascertained by many investigators to be composed largely of ƒ¿-1,6-glucopyranosidic linkage and some of ƒ¿-1 ,4 or ƒ¿-1,3-linkages. Dextransucrase, an enzyme which converts sucrose into dextran as well as fructose approximately equivalent to sucrose as was shown in equation (a), has been found in the cell-free culture fluids of various strains of Leuc. mesenteraides (3, 4) and of Streptococcus bovi s (5). Some of the properties of the isolated enzyme have been described (2, 6-8), but any exact knowledge of the enzymic action on the mechanism of polymerization of sugar has not yet been acquired. In the course of the investigation on the variation in the ratio of carbon assi milated into polysaccharide to the total carbon metabolized in the presence of various inhibitors, such as antibiotics, metallic ions and vitamins under aerobic and anaerobic conditions, using both homopolysaccharide-producing bacteria (Leuc. mesenteroides) and hetero-polysaccharide-producing bacteria (Aerobacter aerogenes). It was found that Leuc. mesenteroid es produced a large amount of riboflavinyl glucoside in sucrose cultures containing riboflavin, whereby the production of dex tran also took place. Riboflavinylglucoside (5•Œ-D-riboflavin-D-glucopyranoside) was first obtained by Whitby (9-11) with acetone-dried powder of rat liver, and then by Katagiri, Tachibana and Yamada from maltose and riboflavin with the action of the enzyme preparations from a mutant strain of Aspergillus oryzae (12, 13), Escherichia coli (14, 15) and from acetone-butanol-producing bacteria (16). It was suggested that riboflavin and riboflavinylglucoside played an important role on glucosyl carrier in 1 鈴 木幸 雄 ,片 桐 英 郎.