title: Structural basis for the bifunctionality of fructose-1,6-bisphosphate aldolase/phosphatase.
abstract: Enzymes catalyse specific reactions and are essential for maintaining life. Although some are referred to as being bifunctional, they consist of either two distinct catalytic domains or a single domain that displays promiscuous substrate specificity. Thus, one enzyme active site is generally responsible for one biochemical reaction. In contrast to this conventional concept, archaeal fructose-1,6-bisphosphate (FBP) aldolase/phosphatase (FBPA/P) consists of a single catalytic domain, but catalyses two chemically distinct reactions of gluconeogenesis: (1) the reversible aldol condensation of dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (GA3P) to FBP; (2) the dephosphorylation of FBP to fructose-6-phosphate (F6P). Thus, FBPA/P is fundamentally different from ordinary enzymes whose active sites are responsible for a specific reaction. However, the molecular mechanism by which FBPA/P achieves its unusual bifunctionality remains unknown. Here we report the crystal structure of FBPA/P at 1.5-Å resolution in the aldolase form, where a critical lysine residue forms a Schiff base with DHAP. A structural comparison of the aldolase form with a previously determined phosphatase form revealed a dramatic conformational change in the active site, demonstrating that FBPA/P metamorphoses its active-site architecture to exhibit dual activities. Thus, our findings expand the conventional concept that one enzyme catalyses one biochemical reaction.
authors: Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors: Shinya
authors: S
authors: Fushinobu
authors: Hiroshi
authors: H
authors: Nishimasu
authors: Daiki
authors: D
authors: Hattori
authors: Hyun-Jin
authors: HJ
authors: Song
authors: Takayoshi
authors: T
authors: Wakagi
mesh_terms: D055162:Biocatalysis; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004099:Dihydroxyacetone Phosphate / Q000378:metabolism; D005634:Fructose-Bisphosphate Aldolase / Q000737:chemistry* / Q000378:metabolism*; D005635:Fructosediphosphates / Q000378:metabolism; D005943:Gluconeogenesis; D005986:Glyceraldehyde 3-Phosphate / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism; D008958:Models, Molecular; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry* / Q000378:metabolism*; D010766:Phosphorylation; D011487:Protein Conformation; D012545:Schiff Bases / Q000737:chemistry / Q000378:metabolism; D016944:Sulfolobus / Q000201:enzymology*
chemical_list: D005635:Fructosediphosphates; D012545:Schiff Bases; D005986:Glyceraldehyde 3-Phosphate; D004099:Dihydroxyacetone Phosphate; D010744:Phosphoric Monoester Hydrolases; D005634:Fructose-Bisphosphate Aldolase; D008274:Magnesium; D008239:Lysine; C029063:fructose-1,6-diphosphate