Comparative anatomy of the aldo–keto reductase superfamily

Abstract

The aldo-keto reductases metabolize a wide range of substrates and are potential drug targets. This protein superfamily includes aldose reductases, aldehyde reductases, hydroxysteroid dehydrogenases and dihydrodiol dehydrogenases. By combining multiple sequence alignments with known three-dimensional structures and the results of site-directed mutagenesis studies, we have developed a structure/function analysis of this superfamily. Our studies suggest that the (alpha/beta)8-barrel fold provides a common scaffold for an NAD(P)(H)-dependent catalytic activity, with substrate specificity determined by variation of loops on the C-terminal side of the barrel. All the aldo-keto reductases are dependent on nicotinamide cofactors for catalysis and retain a similar cofactor binding site, even among proteins with less than 30% amino acid sequence identity. Likewise, the aldo-keto reductase active site is highly conserved. However, our alignments indicate that variation ofa single residue in the active site may alter the reaction mechanism from carbonyl oxidoreduction to carbon-carbon double-bond reduction, as in the 3-oxo-5beta-steroid 4-dehydrogenases (Delta4-3-ketosteroid 5beta-reductases) of the superfamily. Comparison of the proposed substrate binding pocket suggests residues 54 and 118, near the active site, as possible discriminators between sugar and steroid substrates. In addition, sequence alignment and subsequent homology modelling of mouse liver 17beta-hydroxysteroid dehydrogenase and rat ovary 20alpha-hydroxysteroid dehydrogenase indicate that three loops on the C-terminal side of the barrel play potential roles in determining the positional and stereo-specificity of the hydroxysteroid dehydrogenases. Finally, we propose that the aldo-keto reductase superfamily may represent an example of divergent evolution from an ancestral multifunctional oxidoreductase and an example of convergent evolution to the same active-site constellation as the short-chain dehydrogenase/reductase superfamily.

Close kinship of human 20α‐hydroxysteroid dehydrogenase gene with three aldo‐keto reductase genes

“…Before the initiation of parturition, the progesterone level decreases markedly due to 20a-HSD induction, which is a cytosolic enzyme that converts progesterone to the inactive form 20a-hydroxyprogesterone (20a-OHP), in the corpus luteum of rodents (Wiest 1959;Batra et al 1976). Recently, cDNAs encoding rabbit [AKR 1C5] (Lacy et al 1993) and rat [AKR 1C8] (Mao et al 1994;Miura et al 1994) 20a-HSDs were isolated, and 20a-HSD is classi®ed as an aldo-keto reductase (AKR) (1997b; Jez et al 1997a). The AKR superfamily consists of monomeric NAD(P)(H)-dependent oxido-reductases with a broad speci®city of substrates: endogenous substrates, such as steroid hormones and prostaglandins (PGs); and xenobiotics, such as drugs and carcinogens.…”

Cloning and sequencing of the cDNA species for mammalian dimeric dihydrodiol dehydrogenases

“…The sequences of the five dimeric DDs did not show significant similarity to the aldo-keto reductase family proteins including monomeric DDs [11], but Asp-49, Tyr-55 and Lys-91 of the dimeric enzymes (other than rabbit DD) almost correspond to the important residues in the catalysis of the aldo-keto reductase family enzymes [11]. The Tyr residue has been demonstrated by site-directed mutation into Phe to be the catalytic residue of the aldo-keto reductases [43,44].…”

“…The enzyme exists in multiple forms in mammalian tissues. Most of the enzymes purified from various mammalian tissues are monomeric and have been shown to be identical with 3α-, 17β-and 20α-hydroxysteroid dehydrogenases, aldehyde reductase and\or aldose reductase [5][6][7][8][9][10], which are members of the aldo-keto reductase superfamily [11]. In addition to the monomeric enzymes, dimeric DDs composed of 39 kDa subunits have been isolated from rabbit lens [10], monkey kidney [12,13], pig tissues [14] and dog liver [15].…”

“…The dimeric DD does not accept hydroxysteroids as substrates, and oxidizes (k)-(1R,2R)-trans-dihydrodiols of benzene and naphthalene, in contrast with the preference of the monomeric enzymes for the (j)-(1S,2S) isomers [16]. It exhibits high reductase activity for dicarbonyl compounds, aldehydes and ketones [10][11][12][13][14][15]. Thus dimeric DD is also functionally related to carbonyl reductase, which is a member of the Abbreviations used : DD, trans-dihydrodiol dehydrogenase ; GFO, glucose : fructose oxidoreductase ; RACE, rapid amplification of cDNA ends ; RT, reverse-transcriptase.…”

Gene mining-based identification of aldo–keto reductases for highly stereoselective reduction of bulky ketones

“…From the multiple sequence alignment analysis of these polypeptides ( Fig. 1), it was observed that the selected proteins possess a classic Rossmann-fold structure containing the catalytic tetrad D-X 4 -Y-X n -K-X n -H (Jez et al 1997). In addition, the signature sequences (PROSITE Accession No.…”