title: A structural basis for substrate selectivity and stereoselectivity in octopine dehydrogenase from Pecten maximus.
abstract: Octopine dehydrogenase [N(2)-(D-1-carboxyethyl)-L-arginine:NAD(+) oxidoreductase] (OcDH) from the adductor muscle of the great scallop Pecten maximus catalyzes the reductive condensation of l-arginine and pyruvate to octopine during escape swimming. This enzyme, which is a prototype of opine dehydrogenases (OpDHs), oxidizes glycolytically born NADH to NAD(+), thus sustaining anaerobic ATP provision during short periods of strenuous muscular activity. In contrast to some other OpDHs, OcDH uses only l-arginine as the amino acid substrate. Here, we report the crystal structures of OcDH in complex with NADH and the binary complexes NADH/l-arginine and NADH/pyruvate, providing detailed information about the principles of substrate recognition, ligand binding and the reaction mechanism. OcDH binds its substrates through a combination of electrostatic forces and size selection, which guarantees that OcDH catalysis proceeds with substrate selectivity and stereoselectivity, giving rise to a second chiral center and exploiting a "molecular ruler" mechanism.
authors.affiliation: Institute of Biochemistry, Heinrich Heine University, Universitaetsstrasse 1, 40225 Duesseldorf, Germany.
authors.forename: Sander H J
authors.initials: SH
authors.lastname: Smits
authors.forename: Andre
authors.initials: A
authors.lastname: Mueller
authors.forename: Lutz
authors.initials: L
authors.lastname: Schmitt
authors.forename: Manfred K
authors.initials: MK
authors.lastname: Grieshaber
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001120:Arginine / Q000378:metabolism; D001665:Binding Sites; D002384:Catalysis; D018360:Crystallography, X-Ray; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009243:NAD / Q000737:chemistry / Q000378:metabolism; D049910:Pecten / Q000201:enzymology* / Q000235:genetics; D011485:Protein Binding; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D019289:Pyruvic Acid / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D009243:NAD; D019289:Pyruvic Acid; D001120:Arginine; D000594:Amino Acid Oxidoreductases; C021903:D-octopine dehydrogenase