TY - JOUR
T1 - Theoretical calculation of triazolam hydroxylation and endogenous steroid inhibition in the active site of CYP3A4
AU - Torimoto, Nao
AU - Ishii, Itsuko
AU - Hata, Masayuki
AU - Kobayashi, Yukari
AU - Nakamura, Hiroyoshi
AU - Ariyoshi, Noritaka
AU - Kitada, Mitsukazu
PY - 2007/2/1
Y1 - 2007/2/1
N2 - CYP3A4 has unusual kinetic characteristics because it has a large active site. CYP3A4 produced more 4-hydroxytriazolam than α-hydroxytriazolam at concentrations of more than 60 μM triazolam, and different steroids had different inhibitory effects on the system. To clarify these interesting observations, the interactions between substrate and substrate/steroid were investigated by theoretical calculations. When two triazolam molecules were docked into the active site, the distance between the O-atom and the 4-hydroxylated site was less than the distance to the α-hydroxylated site because of interaction between the two triazolam molecules. Estradiol inhibited both α- and 4-hydroxytriazolam formation by 50%. Dehydroepiandrosterone (DHEA) inhibited α-hydroxylation more than 4-hydroxytriazolam formation, whereas aldosterone had no effect. When one triazolam molecule and one steroid molecule were simultaneously docked, estradiol increased the distance between the O-atom and the two hydroxylated sites, DHEA only increased the distance between the O-atom and α-hydroxylated site, and aldosterone did not change the distances. The relevant angles of Fe-O-C in the hydroxylated site of triazolam also widened, together with increased distance. These findings indicate that formation of a substrate and substrate/effector complex in the active site may be a factor for determining the enzyme kinetic parameters of CYP3A4.
AB - CYP3A4 has unusual kinetic characteristics because it has a large active site. CYP3A4 produced more 4-hydroxytriazolam than α-hydroxytriazolam at concentrations of more than 60 μM triazolam, and different steroids had different inhibitory effects on the system. To clarify these interesting observations, the interactions between substrate and substrate/steroid were investigated by theoretical calculations. When two triazolam molecules were docked into the active site, the distance between the O-atom and the 4-hydroxylated site was less than the distance to the α-hydroxylated site because of interaction between the two triazolam molecules. Estradiol inhibited both α- and 4-hydroxytriazolam formation by 50%. Dehydroepiandrosterone (DHEA) inhibited α-hydroxylation more than 4-hydroxytriazolam formation, whereas aldosterone had no effect. When one triazolam molecule and one steroid molecule were simultaneously docked, estradiol increased the distance between the O-atom and the two hydroxylated sites, DHEA only increased the distance between the O-atom and α-hydroxylated site, and aldosterone did not change the distances. The relevant angles of Fe-O-C in the hydroxylated site of triazolam also widened, together with increased distance. These findings indicate that formation of a substrate and substrate/effector complex in the active site may be a factor for determining the enzyme kinetic parameters of CYP3A4.
KW - CYP3A4
KW - Endogenous steroid
KW - Theoretical calculation
KW - Triazolam
UR - http://www.scopus.com/inward/record.url?scp=33846842087&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33846842087&partnerID=8YFLogxK
U2 - 10.1016/j.bbapap.2006.11.009
DO - 10.1016/j.bbapap.2006.11.009
M3 - Article
C2 - 17204458
AN - SCOPUS:33846842087
VL - 1774
SP - 223
EP - 232
JO - Biochimica et Biophysica Acta - Proteins and Proteomics
JF - Biochimica et Biophysica Acta - Proteins and Proteomics
SN - 1570-9639
IS - 2
ER -