TY - JOUR
T1 - Tight-binding inhibition by α-naphthoflavone of human cytochrome P450 1A2
AU - Cho, Uhn Soo
AU - Park, Eun Young
AU - Dong, Mi Sook
AU - Park, Bum Seok
AU - Kim, Keehyuk
AU - Kim, Kyung Hyun
N1 - Funding Information:
Part of this study was supported by a grant (#HMP-98-D-5-0046) from the R&D Project, the Ministry of Health and Welfare, Korea. USC, EYP, and BSP also received additional support from the Brain Korea 21 program of the Ministry of Education.
PY - 2003/5/30
Y1 - 2003/5/30
N2 - Human cytochrome P450 (P450) enzymes exhibit remarkable diversity in their substrate specificities, participating in oxidation reactions of a wide range of xenobiotic drugs. Previously, we reported that α-naphthoflavone (ANF) is bound to the recombinant P450 1A2 tightly and stabilizes an overall enzyme conformation. The present study is designed to determine the type of P450 1A2 inhibition exerted by ANF, using two different substrates of P450 1A2, 7-ethoxycoumarin (EOC) and 7-ethoxyresorufin (EOR). ANF is generally known as a competitive inhibitor of the enzyme. However, in our tight-binding enzyme kinetics study, ANF acts as noncompetitive inhibitor in 7-ethoxycoumarin O-deethylation (ECOD) (Ki=55.0 nM), but as competitive inhibitor in 7-ethoxyresorufin O-deethylation (EROD) (Ki=1.4 nM). Based on homology modeling studies, ANF is positioned to bind to a hydrophobic cavity next to the active site where it may cause a direct effect on substrate binding. It is agreed with the predicted binding site of ANF in P450 3A4, in which ANF is rather known as a stimulating modulator. Our results suggest that ANF binds near the active site of P450 1A2 and exhibits differential inhibition mechanisms, possibly depending on the molecular structure of the substrate.
AB - Human cytochrome P450 (P450) enzymes exhibit remarkable diversity in their substrate specificities, participating in oxidation reactions of a wide range of xenobiotic drugs. Previously, we reported that α-naphthoflavone (ANF) is bound to the recombinant P450 1A2 tightly and stabilizes an overall enzyme conformation. The present study is designed to determine the type of P450 1A2 inhibition exerted by ANF, using two different substrates of P450 1A2, 7-ethoxycoumarin (EOC) and 7-ethoxyresorufin (EOR). ANF is generally known as a competitive inhibitor of the enzyme. However, in our tight-binding enzyme kinetics study, ANF acts as noncompetitive inhibitor in 7-ethoxycoumarin O-deethylation (ECOD) (Ki=55.0 nM), but as competitive inhibitor in 7-ethoxyresorufin O-deethylation (EROD) (Ki=1.4 nM). Based on homology modeling studies, ANF is positioned to bind to a hydrophobic cavity next to the active site where it may cause a direct effect on substrate binding. It is agreed with the predicted binding site of ANF in P450 3A4, in which ANF is rather known as a stimulating modulator. Our results suggest that ANF binds near the active site of P450 1A2 and exhibits differential inhibition mechanisms, possibly depending on the molecular structure of the substrate.
KW - Human cytochrome P450 1A2
KW - Tight-binding inhibition
KW - α-Naphthoflavone
UR - http://www.scopus.com/inward/record.url?scp=1242318619&partnerID=8YFLogxK
U2 - 10.1016/S1570-9639(03)00148-1
DO - 10.1016/S1570-9639(03)00148-1
M3 - Article
C2 - 12758162
AN - SCOPUS:1242318619
VL - 1648
SP - 195
EP - 202
JO - Biochimica et Biophysica Acta - Proteins and Proteomics
JF - Biochimica et Biophysica Acta - Proteins and Proteomics
SN - 1570-9639
IS - 1-2
ER -