Dd. Song et Na. Jacques, Purification and enzymic properties of the fructosyltransferase of Streptococcus salivarius ATCC 25975, BIOCHEM J, 341, 1999, pp. 285-291
The recombinant fructosyltransferase (Ftf) of Streptococcus salivarius was
expressed in Escherichia coli and purified to electrophoretic homogeneity a
fter a combination of adsorption, ion-exchange and gel-filtration chromatog
raphy. The N-terminal signal sequence of the Ftf was removed by E. coli at
the same site as in its natural host. The purified Ftf exhibited maximum ac
tivity at pH 6.0 and 37 degrees C, was activated by Ca2+, but inhibited by
the metal ions Cu2+, Zn2+, Hg2+ and Fe3+. The enzyme catalysed the transfer
of the fructosyl moiety of sucrose to a number of accepters, including wat
er, glucose and sucrose via a Ping Pong mechanism involving a fructosyl-enz
yme intermediate. While this mechanism of catalysis is utilized by the leva
nsucrases of Bacillus subtilis and Acetobacter diazotrophicus and the value
s of the kinetic constants for the three enzymes are similar, sucrose was a
far more efficient fructosyl-acceptor for the Ftf of S. salivarius than fo
r the two other enzymes.