title: DXP reductoisomerase: reaction of the substrate in pieces reveals a catalytic role for the nonreacting phosphodianion group.
abstract: The role of the nonreacting phosphodianion group of 1-deoxy-d-xylulose-5-phosphate (DXP) in catalysis by DXP reductoisomerase (DXR) was investigated for the reaction of the "substrate in pieces". The truncated substrate 1-deoxy-l-erythrulose is converted by DXR to 2-C-methylglycerol with a kcat/Km that is 10(6)-fold lower than that for DXP. Phosphite dianion was found to be a nonessential activator, providing 3.2 kcal/mol of transition state stabilization for the truncated substrate. These results implicate a phosphate-driven conformational change involving loop closure over the DXR active site to generate an environment poised for catalysis.
authors.affiliation: Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA.
authors.forename: Svetlana A
authors.initials: SA
authors.lastname: Kholodar
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Murkin
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000737:chemistry / Q000378:metabolism*; D020134:Catalytic Domain; D007700:Kinetics; D008958:Models, Molecular; D009169:Mycobacterium tuberculosis / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D010428:Pentosephosphates / Q000737:chemistry / Q000378:metabolism*; D010710:Phosphates / Q000737:chemistry / Q000378:metabolism; D017905:Phosphites / Q000737:chemistry / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: C109460:1-deoxylulose 5-phosphate; D010428:Pentosephosphates; D010710:Phosphates; D017905:Phosphites; C114231:1-deoxy-D-xylulose 5-phosphate reductoisomerase; D019747:Aldose-Ketose Isomerases