Catalyzes the reversible formation of fructose 6-phosphate from dihydroxyacetone (DHA) and D-glyceraldehyde 3-phosphate via an aldolization reaction. Can utilize several aldehydes as acceptor compounds in vitro, and hydroxyacetone (HA) or 1-hydroxy-butan-2-one as alternative donor substrate. Is also able to catalyze the direct stereoselective self-aldol addition of glycolaldehyde to furnish D-(-)-threose, and cross-aldol reactions of glycolaldehyde to other aldehyde acceptors. Is not able to cleave fructose, fructose 1-phosphate, glucose 6-phosphate, sedoheptulose 1,7-bisphosphate, xylulose 5-phosphate, ribulose 5-phosphate, and fructose 1,6-bisphosphate; cannot use dihydroxyacetone phosphate as donor compound nor D-glyceraldehyde as acceptor. Does not display transaldolase activity. beta-D-fructose 6-phosphate = D-glyceraldehyde 3-phosphate + dihydroxyacetone Inhibited by glycerol, inorganic phosphate and arabinose 5-phosphate. kcat is 1.31 sec(-1), 0.82 sec(-1) and 0.63 sec(-1) using glyceraldehyde 3-phosphate as acceptor substrate, and dihydroxyacetone, hydroxyacetone or 1-hydroxy-butan-2-one as donor substrate, respectively (at 25 degrees Celsius and pH 8.5). Optimum pH is about 8.5. Active from pH 6 to 12. Displays a broad temperature optimum and is active in the range from 20 to 75 degrees Celsius. Although no significant loss of activity is detected after 600 hours of incubation at 45 degrees Celsius (at pH 8.0), the respective half-lives of the enzyme are 200 hours at 55 degrees Celsius, 30 hours at 65 degrees Celsius, and 16 hours at 75 degrees Celsius. Homodecamer. Five subunits are arranged as a pentamer, and two ring-like pentamers pack like a donut to form the decamer. Is an interesting tool in chemoenzymatic synthesis for the construction of chiral complex polyhydroxylated sugar-type structures. The use of hydroxyacetone (acetol) as a donor compound allows access to various 1-deoxysugars. Can also be used for the synthesis of a broad range of iminocyclitols, that are potent glycosidase and glycosyltransferase inhibitors, from dihydroxyacetone, hydroxyacetone or 1-hydroxy-butan-2-one as donor substrate, and a range of acceptor substrates. Is not inhibited by EDTA which points to a metal-independent mode of action. Belongs to the transaldolase family. Type 3A subfamily.