The mechanism of dextransucrase action

摘要: Abstract Dextransucrase from Leuconostoc mesenteroides B-512 catalyzes the polymerization of dextran sucrose. The resulting has 95% α-1 → 6 linkages and 5% 3 branch linkages. A purified dextransucrase was insolubilized on Bio-Gel P-2 beads (BGD, Bio-Gel-dextransucrase). BGD labeled by incubating it with a very low concentration [ 14 C]sucrose or first charged nonlabeled sucrose then C]sucrose. After extensive washings buffer, C label remained attached to BGD. This material previously shown be C]dextran postulated covalently at reducing end active site enzyme. When incubated molecular weight (acceptor dextran) all BGD-bound released as whereas essentially no when in buffer alone under comparable conditions. slightly branched hydrolysis an exodextranase. Acetolysis gave 7.3% radioactivity nigerose. Reduction sodium borohydride, followed acid hydrolysis, glucose, indicating that nigerose exclusively nonreducing glucose unit. These results indicated being virtue action this formation new linkage. mehanism for branching is proposed which -OH acceptor acts nucleophile 1 dextranosyl-dextransucrase complex, thereby displacing forming It argued biosynthesis does not require separate enzyme but can take place reactions complex.