Two dextransucrase genes, dsrS and dsrT5, from Leuconostoc mesenteroides NR
RL B-512F were expressed in Escherichia coli, and recombinant dsrT5 dextran
sucrase was shown to produce a water-insoluble glucan. In contrast, native
dextran from L. mesenteroides B-512F is water-soluble. The water-insoluble
glucan was shown by C-13 NMR and glycosyl-linkage composition analysis to c
ontain about 50% 6-linked Glcp and 40% 3-linked Glcp. The 'primitive' B-512
F strain is suggested to have produced water-insoluble glucan containing 3-
linked Glcp. The glucans produced by dextransucrases expressed in E. coli c
ontained 4-linked Glcp, as shown by glycosyl-linkage composition analysis.
The amount of 4-linked Glcp was increased when the truncated, water-insolub
le, glucan-producing dextransucrase, which does not have C-terminal repeati
ng units, was added to the water-soluble, glucan-producing dextransucrase.
Trace amounts of 4-linked Glcp were also detected in the dextran obtained f
rom the B-512F culture supernatant, in dextran produced by dextransucrase p
urified from the B-512F strain culture supernatant, and in clinical dextran
. The results of glycosyl-linkage composition analysis suggest that dextran
sucrases produce 4-linked Glcp as well as 6- and 3-linked Glcp. (C) 2001 Pu
blished by Elsevier Science Ltd.