The combinatorial modulation of inter- and intra-subunit interactions of decameric D-fructose-6-phosphate aldolase A (FSAA) generated a triple-site variant I31T/Q59T/I195Q FSAA with 27- to 278-fold improvement in activity towards target heteroaromatic aldehydes. X-ray crystallographic data and molecular dynamics simulations ascribed the enhanced activity to the pronounced flexibility of the interface region between subunits, the expanded substrate entrance and binding pocket, and enhanced proton transfer, unambiguously demonstrating the efficiency of this strategy for engineering multimeric enzymes.