title: New enzymatic assay for the AKR1C enzymes.
abstract: The imbalance in expression of the human aldo-keto reductases AKR1C1-AKR1C3 is related to different hormone dependent and independent cancers and some other diseases. The AKR1C1-3 enzymes thus represent emerging targets for the development of new drugs. Currently, various enzymatic assays are used in the search for AKR1C inhibitors, and consequently the results of different research groups are not necessarily comparable. During our recent search for AKR1C inhibitors, we found a cyclopentanol derivative (2-(4-chlorobenzylidene)cyclopentanol, CBCP-ol) and its respective cyclopentanone counterpart (2-(4-chlorobenzylidene)cyclopentanone, CBCP-one) that acted as AKR1C substrates. We determined the kinetic parameters KM, kcat and kcat/KM for oxidation of CBCP-ol and reduction of CBCP-one by AKR1C enzymes in the presence of NAD(+)/NADP(+) and NADH/NADPH, respectively. The catalytic efficiencies for the oxidation of CBCP-ol in the presence of NAD(+) or NADP(+) were in general higher when compared to the catalytic efficiencies for reduction of CBCP-one in the presence of NADH or NADPH. When NADPH was used, as compared to NADH, the reductions of CBCP-one by AKR1C1, AKR1C2 and AKR1C3 were 14-, 51- and 31-fold more efficient, respectively. When comparing to oxidations of the well-known artificial substrates, 1-acenaphthenol and S-tetralol, we observed similar catalytic efficiencies as for CBCP-ol oxidation with NAD(+) and NADP(+). The comparison of CBCP-one reduction with NADPH to reductions of physiological substrates revealed in general higher efficiencies, except for reduction of 9-cis-retinaldehyde by AKR1C3. This NADPH-dependent reduction of CBCP-one was then used to re-evaluate inhibitory potencies of the known inhibitors of the target AKR1C3 and the anti-target AKR1C2, medroxyprogesterone acetate and ursodeoxycholic acid, respectively, showing Ki constants similar to the reported values. Our data thus confirm that the new enzymatic assays with two cyclopentane substrates CBP-ol and CBP-one, and especially reduction of CBCP-one with NADPH, are appropriate for the evaluation of AKR1C inhibitors.
authors.affiliation: Institute of Biochemistry, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.
authors.forename: Nataša
authors.initials: N
authors.lastname: Beranič
authors.forename: Bogdan
authors.initials: B
authors.lastname: Stefane
authors.forename: Boris
authors.initials: B
authors.lastname: Brus
authors.forename: Stanislav
authors.initials: S
authors.lastname: Gobec
authors.forename: Tea Lanišnik
authors.initials: TL
authors.lastname: Rižner
mesh_terms: D015089:20-Hydroxysteroid Dehydrogenases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D015096:3-Hydroxysteroid Dehydrogenases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D000429:Alcohol Oxidoreductases / Q000378:metabolism; D000449:Aldehyde Reductase; D000074425:Aldo-Keto Reductase Family 1 Member C3; D000074408:Aldo-Keto Reductases; D002384:Catalysis; D003517:Cyclopentanes / Q000494:pharmacology; D057075:Enzyme Assays / Q000379:methods*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D006911:Hydroxyprostaglandin Dehydrogenases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D007700:Kinetics; D017258:Medroxyprogesterone Acetate / Q000494:pharmacology; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D014580:Ursodeoxycholic Acid / Q000494:pharmacology
chemical_list: D003517:Cyclopentanes; D004791:Enzyme Inhibitors; D009243:NAD; C016327:cyclopentanol; C007201:cyclopentanone; D009249:NADP; D014580:Ursodeoxycholic Acid; D017258:Medroxyprogesterone Acetate; D015096:3-Hydroxysteroid Dehydrogenases; D000429:Alcohol Oxidoreductases; D015089:20-Hydroxysteroid Dehydrogenases; C115140:3 alpha-beta, 20 beta-hydroxysteroid dehydrogenase; D000074408:Aldo-Keto Reductases; D006911:Hydroxyprostaglandin Dehydrogenases; D000449:Aldehyde Reductase; C487341:AKR1C3 protein, human; D000074425:Aldo-Keto Reductase Family 1 Member C3