title: Chiral inversion of RS-8359: a selective and reversible MAO-A inhibitor via oxido-reduction of keto-alcohol.
abstract: RS-8359, (+/-)-4-(4-cyanoanilino)-5,6-dihydro-7-hydroxy-7H-cyclopenta[d]-pyrimidine is a selective and reversible MAO-A inhibitor. The (S)-enantiomer of RS-8359 has been demonstrated to be inverted to the (R)-enantiomer after oral administration to rats. In the current study, we investigated the chiral inversion mechanism and the properties of involved enzymes using rat liver subcellular fractions. The 7-hydroxy function of RS-8359 was oxidized at least by the two different enzymes. The cytosolic enzyme oxidized enantiospecifically the (S)-enantiomer with NADP as a cofactor. On the other hand, the microsomal enzyme catalyzed more preferentially the oxidation of the (S)-enantiomer than the (R)-enantiomer with NAD as a cofactor. With to product enantioselectivity of reduction of the 7-keto derivative, it was found that only the alcohol bearing (R)-configuration was formed by the cytosolic enzyme with NADPH and the microsomal enzyme with NADH at almost equal rate. The reduction rate was much larger than the oxidation rate of 7-hydroxy group. The results suggest that the chiral inversion might occur via an enantioselectivity of consecutive two opposing reactions, oxidation and reduction of keto-alcohol group. In this case, the direction of chiral inversion from the (S)-enantiomer to the (R)-enantiomer is governed by the enantiospecific reduction of intermediate 7-keto group to the alcohol with (R)-configuration. The enzyme responsible for the enantiospecific reduction of the 7-keto group was purified from rat liver cytosolic fractions and identified as 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) via database search of peptide mass data obtained by nano-LC/MS/MS.
authors.affiliation: Department of Biopharmaceutics, Tohoku Pharmaceutical University, Sendai, Japan.
authors.forename: Kunio
authors.initials: K
authors.lastname: Itoh
authors.forename: Kouichi
authors.initials: K
authors.lastname: Hoshino
authors.forename: Asuka
authors.initials: A
authors.lastname: Endo
authors.forename: Tasuku
authors.initials: T
authors.lastname: Asakawa
authors.forename: Kazumi
authors.initials: K
authors.lastname: Yamakami
authors.forename: Chisa
authors.initials: C
authors.lastname: Noji
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kosaka
authors.forename: Yorihisa
authors.initials: Y
authors.lastname: Tanaka
mesh_terms: D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific) / Q000737:chemistry / Q000378:metabolism; D000284:Administration, Oral; D000438:Alcohols / Q000378:metabolism*; D000818:Animals; D002853:Chromatography, Liquid; D003600:Cytosol / Q000201:enzymology; D004591:Electrophoresis, Polyacrylamide Gel; D008099:Liver / Q000201:enzymology; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism; D015394:Molecular Structure; D008996:Monoamine Oxidase Inhibitors / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D036103:Nanotechnology; D009570:Nitriles / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D010084:Oxidation-Reduction; D011743:Pyrimidines / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013237:Stereoisomerism; D013347:Subcellular Fractions / Q000201:enzymology; D013379:Substrate Specificity; D053719:Tandem Mass Spectrometry
chemical_list: D000438:Alcohols; D008996:Monoamine Oxidase Inhibitors; D009570:Nitriles; D011743:Pyrimidines; D009243:NAD; D009249:NADP; C059590:RS 8359; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific)