title: Human and rodent aldo-keto reductases from the AKR1B subfamily and their specificity with retinaldehyde.
abstract: NADP(H)-dependent cytosolic aldo-keto reductases (AKR) are mostly monomeric enzymes which fold into a typical (α/β)(8)-barrel structure. Substrate specificity and inhibitor selectivity are determined by interaction with residues located in three highly variable loops (A, B, and C). Based on sequence identity, AKR have been grouped into families, namely AKR1-AKR15, containing multiple subfamilies. Two human enzymes from the AKR1B subfamily (AKR1B1 and AKR1B10) are of special interest. AKR1B1 (aldose reductase) is related to secondary diabetic complications, while AKR1B10 is induced in cancer cells and is highly active with all-trans-retinaldehyde. Residues interacting with all-trans-retinaldehyde and differing between AKR1B1 and AKR1B10 are Leu125Lys and Val131Ala (loop A), Leu301Val, Ser303Gln, and Cys304Ser (loop C). Recently, we demonstrated the importance of Lys125 as a determinant of AKR1B10 specificity for retinoids. Residues 301 and 304 are also involved in interactions with substrates or inhibitors, and thus we checked their contribution to retinoid specificity. We also extended our study with retinoids to rodent members of the AKR1B subfamily: AKR1B3 (aldose reductase), AKR1B7 (mouse vas deferens protein), AKR1B8 (fibroblast-growth factor 1-regulated protein), and AKR1B9 (Chinese hamster ovary reductase), which were tested against all-trans isomers of retinaldehyde and retinol. All enzymes were active with retinaldehyde, but with k(cat) values (0.02-0.52 min(-1)) much lower than that of AKR1B10 (27 min(-1)). None of the enzymes showed oxidizing activity with retinol. Since these enzymes (except AKR1B3) have Lys125, other residues should account for retinaldehyde specificity. Here, by using site-directed mutagenesis and molecular modeling, we further delineate the contribution of residues 301 and 304. We demonstrate that besides Lys125, Ser304 is a major structural determinant for all-trans-retinaldehyde specificity of AKR1B10.
authors.affiliation: Department of Biochemistry and Molecular Biology, Universitat Autònoma de Barcelona, Barcelona, Spain.
authors.forename: F Xavier
authors.initials: FX
authors.lastname: Ruiz
authors.forename: Armando
authors.initials: A
authors.lastname: Moro
authors.forename: Oriol
authors.initials: O
authors.lastname: Gallego
authors.forename: Albert
authors.initials: A
authors.lastname: Ardèvol
authors.forename: Carme
authors.initials: C
authors.lastname: Rovira
authors.forename: J Mark
authors.initials: JM
authors.lastname: Petrash
authors.forename: Xavier
authors.initials: X
authors.lastname: Parés
authors.forename: Jaume
authors.initials: J
authors.lastname: Farrés
mesh_terms: D000449:Aldehyde Reductase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019295:Computational Biology; D006224:Cricetinae; D006801:Humans; D007700:Kinetics; D051379:Mice; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009249:NADP / Q000378:metabolism; D011487:Protein Conformation; D051381:Rats; D012172:Retinaldehyde / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D009249:NADP; D000449:Aldehyde Reductase; D012172:Retinaldehyde