title: Crystal structure of a NAD-dependent D-glycerate dehydrogenase at 2.4 A resolution.
abstract: D-Glycerate dehydrogenase (GDH) catalyzes the NADH-linked reduction of hydroxypyruvate to D-glycerate. GDH is a member of a family of NAD-dependent dehydrogenases that is characterized by a specificity for the D-isomer of the hydroxyacid substrate. The crystal structure of the apoenzyme form of GDH from Hyphomicrobium methylovorum has been determined by the method of isomorphous replacement and refined at 2.4 A resolution using a restrained least-squares method. The crystallographic R-factor is 19.4% for all 24,553 measured reflections between 10.0 and 2.4 A resolution. The GDH molecule is a symmetrical dimer composed of subunits of molecular mass 38,000, and shares significant structural homology with another NAD-dependent enzyme, formate dehydrogenase. The GDH subunit consists of two structurally similar domains that are approximately related to each other by 2-fold symmetry. The domains are separated by a deep cleft that forms the putative NAD and substrate binding sites. One of the domains has been identified as the NAD-binding domain based on its close structural similarity to the NAD-binding domains of other NAD-dependent dehydrogenases. The topology of the second domain is different from that found in the various catalytic domains of other dehydrogenases. A model of a ternary complex of GDH has been built in which putative catalytic residues are identified based on sequence homology between the D-isomer specific dehydrogenases. A structural comparison between GDH and L-lactate dehydrogenase indicates a convergence of active site residues and geometries for these two enzymes. The reactions catalyzed are chemically equivalent but of opposing stereospecificity. A hypothesis is presented to explain how the two enzymes may exploit the same coenzyme stereochemistry and a similar spatial arrangement of catalytic residues to carry out reactions that proceed to opposite enantiomers.
authors.affiliation: Blackett Laboratory, Imperial College, London, England.
authors.forename: J D
authors.initials: JD
authors.lastname: Goldberg
authors.forename: T
authors.initials: T
authors.lastname: Yoshida
authors.forename: P
authors.initials: P
authors.lastname: Brick
mesh_terms: D000595:Amino Acid Sequence; D001051:Apoenzymes / Q000737:chemistry / Q000235:genetics; D001419:Bacteria / Q000201:enzymology / Q000235:genetics; D001665:Binding Sites / Q000235:genetics; D002237:Carbohydrate Dehydrogenases / Q000737:chemistry* / Q000235:genetics; D003460:Crystallization; D018360:Crystallography, X-Ray; D007770:L-Lactate Dehydrogenase / Q000737:chemistry / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D008970:Molecular Weight; D009243:NAD / Q000737:chemistry; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D013237:Stereoisomerism
chemical_list: D001051:Apoenzymes; D009243:NAD; D002237:Carbohydrate Dehydrogenases; D007770:L-Lactate Dehydrogenase; C020669:Glycerate dehydrogenase