Active-site remodelling in the bifunctional fructose-1,6-bisphosphate aldolase/phosphatase.
09.10.2011
Du J, Say RF, Lü W, Fuchs G, Einsle O
Nature. 2011;478(7370):534-7
Fructose-1,6-bisphosphate aldolase/phosphatase (FBPAP) is a bifunctional, thermostable enzyme that catalyzes two subsequent steps in gluconeogenesis in most archaea and in deeply branching bacterial lineages. It mediates the aldol condensation of heat-labile dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (GAP) to FBP, as well as the subsequent, irreversible hydrolysis of the product to yield the stable fructose-6-phosphate (F6P) and inorganic phosphate; no reaction intermediates are released.
We have solve the structure of FBPAP in complex with various substrates and intermediates and present a series of structural snapshots of the reaction that reveal a substantial remodeling of the active site through the movement of loop regions that create different catalytic functionalities at the same location. In conjunction with mutagenesis data this pinpoints the residues required for the two reaction steps and shows that the sequential binding of additional Mg2+ cations reversibly facilitates the reaction. FBP aldolase/phosphatase is an ancestral gluconeogenic enzyme optimized for high ambient temperatures, and our work resolves how consecutive structural rearrangements reorganize the catalytic center of the protein in order to carry out two canonical reactions in a very non-canonical type of bifunctionality.
