Catalyzes the synthesis of alpha-glucan from sucrose. Catalyzes, in addition, sucrose hydrolysis, maltose and maltotriose synthesis by successive transfers of the glucosyl moiety of sucrose onto the released glucose, and finally turanose and trehalulose synthesis, these two sucrose isomers being obtained by glucosyl transfer onto fructose. [(1->4)-alpha-D-glucosyl](n) + sucrose = [(1->4)-alpha-D-glucosyl](n+1) + D-fructose Amylosucrase favors hydrolysis at low sucrose concentrations, and polymerization at high sucrose concentrations. Competitively inhibited by fructose. This enzyme does not present a classic Michaelis-Menten behavior for sucrose consumption, that could be related to the presence of a second sucrose binding site. Nevertheless, it is possible to model sucrose consumption rate versus sucrose concentration by two different Michaelis-Menten equations whose apparent kinetic constants are given just above. Monomer. Like the recombinant protein expressed in E.coli, the amylosucrase may be secreted in N.polysaccharea without cleavage of a signal sequence. Belongs to the glycosyl hydrolase 13 family.