TY - JOUR
T1 - Polymorphisms in P450 CYP1B1 affect the conversion of estradiol to the potentially carcinogenic metabolite 4-hydroxyestradiol
AU - Li, Dongtao N.
AU - Seidel, Albrecht
AU - Pritchard, Michael P.
AU - Wolf, C. Roland
AU - Friedberg, Thomas
PY - 2000/6
Y1 - 2000/6
N2 - Most drug metabolizing cytochrome P450s (P450) are predominantly expressed in the liver. In contrast, human CYP1B1 is an extrahepatic P450 which is overexpressed in many tumours and has been strongly implicated in the activation of carcinogens. Rare allelic variants of the CYP1B1 gene which encode an inactive protein have been identified. However, four polymorphisms which most likely do not abolish functionality have been described. In this report, we have characterized the functional consequences of these. A CYP1B1 cDNA, identical to a cDNA published previously, served as a template to introduce allelic changes either separately or in combination. The resulting effects on CYP1B1 activity were determined in membranes isolated from Escherichia coli which coexpressed CYP1B1 together with P450 reductase. None of the allelic changes affected the CYP1B1 expression level. The allelic changes Arg48 to Gly, Ala119 to Ser and Asn453 to Ser had little influence on the V(max) and the K(m) of the CYP1B1 mediated 2- and 4-hydroxylation of estradiol. In contrast, the K(m) of these metabolic pathways was increased at least three-fold by the allelic change Val432 to Leu or by simultaneously changing Val432 to Leu and Asn453 to Ser. However, these alterations had little effect on the kinetic parameters of other CYP1B1 mediated reactions such as the epoxidation of (-)-trans-(7R,8R)-benzo[a]pyrene 7,8-dihydrodiol as determined by (r-7,t-8,t-9,c-10)-benzo[a]pyrene tetraol formation, or such as the O-dealkylation of ethoxyresorufin and the 1'-hydroxylation of bufuralol. Molecular modelling suggests that amino acid residue 432 of CYP1B1 may be involved in the interaction between CYP1B1 and P450 reductase. Since 4-hydroxyestradiol has been implicated in hormonal carcinogenesis and CYP1B1 is expressed in target tissues, the data presented demonstrate that polymorphisms in CYP1B1 have the potential to affect disease susceptibility. (C) 2000 Lippincott Williams and Wilkins.
AB - Most drug metabolizing cytochrome P450s (P450) are predominantly expressed in the liver. In contrast, human CYP1B1 is an extrahepatic P450 which is overexpressed in many tumours and has been strongly implicated in the activation of carcinogens. Rare allelic variants of the CYP1B1 gene which encode an inactive protein have been identified. However, four polymorphisms which most likely do not abolish functionality have been described. In this report, we have characterized the functional consequences of these. A CYP1B1 cDNA, identical to a cDNA published previously, served as a template to introduce allelic changes either separately or in combination. The resulting effects on CYP1B1 activity were determined in membranes isolated from Escherichia coli which coexpressed CYP1B1 together with P450 reductase. None of the allelic changes affected the CYP1B1 expression level. The allelic changes Arg48 to Gly, Ala119 to Ser and Asn453 to Ser had little influence on the V(max) and the K(m) of the CYP1B1 mediated 2- and 4-hydroxylation of estradiol. In contrast, the K(m) of these metabolic pathways was increased at least three-fold by the allelic change Val432 to Leu or by simultaneously changing Val432 to Leu and Asn453 to Ser. However, these alterations had little effect on the kinetic parameters of other CYP1B1 mediated reactions such as the epoxidation of (-)-trans-(7R,8R)-benzo[a]pyrene 7,8-dihydrodiol as determined by (r-7,t-8,t-9,c-10)-benzo[a]pyrene tetraol formation, or such as the O-dealkylation of ethoxyresorufin and the 1'-hydroxylation of bufuralol. Molecular modelling suggests that amino acid residue 432 of CYP1B1 may be involved in the interaction between CYP1B1 and P450 reductase. Since 4-hydroxyestradiol has been implicated in hormonal carcinogenesis and CYP1B1 is expressed in target tissues, the data presented demonstrate that polymorphisms in CYP1B1 have the potential to affect disease susceptibility. (C) 2000 Lippincott Williams and Wilkins.
KW - Chemical carcinogenesis
KW - Cytochrome P450
KW - Polymorphic drug oxidations
KW - Steroid metabolism
UR - http://www.scopus.com/inward/record.url?scp=0034039377&partnerID=8YFLogxK
U2 - 10.1097/00008571-200006000-00008
DO - 10.1097/00008571-200006000-00008
M3 - Article
C2 - 10862525
AN - SCOPUS:0034039377
VL - 10
SP - 343
EP - 353
JO - Pharmacogenetics
JF - Pharmacogenetics
SN - 0960-314X
IS - 4
ER -