Cl. Simpson et al., 4 GLUCOSYLTRANSFERASES, GTFJ, GTFK, GTFL AND GTFM, FROM STREPTOCOCCUS-SALIVARIUS ATCC-25975, Microbiology, 141, 1995, pp. 1451-1460
The four recombinant glucosyltransferases (GTFs), GtfJ, GtfK, GtfL and
GtfM, that had previously been cloned from Streptococcus salivarius A
TCC 25975, were individually expressed in Escherichia coli and their g
lucan products and kinetic properties were analysed. GtfJ was a primer
-dependent GTF which synthesized an insoluble glucan composed mainly o
f alpha-(1 --> 3)-linked glucosyl residues in the presence of dextran
T-10. GtfK was primer-stimulated, and produced a linear soluble dextra
n without any detectable branch points both in the absence and in the
presence of dextran T-10. GtfL was primer-independent and produced a m
ixed-linkage insoluble glucan composed of approximately equal proporti
ons of alpha-(1 --> 3)- and alpha-(1 --> 6)-linked glucosyl residues.
GtfL was inhibited by dextran T-10. GtfM was primer-independent and pr
oduced a soluble dextran with approximately 5 % alpha-(1 --> 3)-linked
glucosyl residues. GtfM was essentially unaffected by the presence of
dextran T-10. The results confirmed that each enzyme represented one
of the four possible combinations of primer-dependency and product sol
ubility and that each possessed unique biosynthetic properties. The so
luble dextrans formed by GtfK end GtfM, as well as the mixed-linkage i
nsoluble glucan formed by GtfL, were also capable of acting as primers
for the primer-dependent GtfJ and the primer-stimulated GtfK. Unexpec
tedly, the linear dextran produced by GtfK was by far the least effect
ive either at priming itself or at activating and priming the primer-d
ependent GtfJ.