Quinone reductase 2 substrate specificity and inhibition pharmacology.
Quinone reductase 2 is a mammalian cytosolic FAD-dependent enzyme, the activity of which is not supported by conventional nicotinamide nucleotides. An endobiotic substrate has never been reported for this enzyme nor a set of molecular tools, such as inhibitors. In the present work, we used the recombinant human enzyme, expressed in CHO cells for the systematic screening of both co-substrates and substrates. The co-substrates survey showed that the natural occurring compound, N-ribosylnicotinamide, was a poor co-substrate. The synthetic N-benzylnicotinamide is a better one compared to any other compounds tested. We found that tetrahydrofolic acid acted as a co-substrate for the reduction of menadione catalysed by quinone reductase 2, although with poor potency (Km approximately 2 mM). Among a series of commercially available quinones, a single one was found to be substrate of quinone reductase 2, in the presence of N-benzyldihydronicotinamide: coenzyme Q0. Finally, we tested a series of 197 flavonoids as potential inhibitors. We found apigenin, genistein or kaempferol as good inhibitor of quinone reductase 2 activity with IC50 in the 100 nM range. These compounds, co-substrate, substrate and inhibitors will permit to better know this enzyme, the role of which is still poorly understood.
Boutin
Jean A
JA
Pharmacologie Moléculaire et Cellulaire, Institut de Recherches Servier, 125 chemin de Ronde, 78290 Croissy-sur-Seine, France. jean.boutin@fr.netgrs.com
Chatelain-Egger
Florence
F
Vella
Fanny
F
Delagrange
Philippe
P
Ferry
Gilles
G
D000818:Animals; D016466:CHO Cells; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D006224:Cricetinae; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D047309:Flavones / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D008322:Mammals; D011808:Quinone Reductases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
D004791:Enzyme Inhibitors; D047309:Flavones; D011994:Recombinant Proteins; D011808:Quinone Reductases