Functional characterization of human and cynomolgus monkey UDP-glucuronosyltransferase 1A1 enzymes.
OBJECTIVE
UDP-glucuronosyltransferase 1A1 (UGT1A1) plays important roles in the glucuronidation of various drugs and endogenous substances. Cynomolgus monkeys are regarded as experimental animals closer to humans in studies on safety evaluation and biotransformation for drug development. In this study, the similarities and differences in the enzymatic properties of UGT1A1 between humans and cynomolgus monkeys were precisely identified.


METHODS
Human and cynomolgus monkey UGT1A1s (humUGT1A1 and monUGT1A1, respectively) were cloned, and the corresponding proteins were heterologously expressed in insect cells. The enzymatic properties of UGT1A1 proteins were characterized by kinetic analysis of 7-hydroxy-4-trifluoromethylcoumarin (7-HFC), estradiol at 3-hydroxy position (E-3OH) and 7-ethyl-10-hydroxycamptothecin (SN-38) glucuronidation.


RESULTS
There were no significant differences in the levels of kinetic parameters for 7-HFC, E-3OH and SN-38 glucuronidation between humans and cynomolgus monkeys in both enzyme sources of liver microsomes and recombinant UGT1A1s. 7-HFC and E-3OH glucuronidation by human liver microsomes exhibited biphasic and sigmoidal kinetics, respectively, whereas the kinetics by cynomolgus monkey liver microsomes fitted the typical Michaelis-Menten model. SN-38 glucuronidation by human and cynomolgus monkey liver microsomes exhibited autoactivation kinetics. In recombinant UGT1A1 enzymes expressed in insect cells, the kinetics of 7-HFC, E-3OH and SN-38 glucuronidation fitted the substrate inhibition (7-HFC glucuronidation) or Hill equation (E-3OH and SN-38 glucuronidation), and each glucuronidation showed the same kinetic profile between humans and cynomolgus monkeys.


CONCLUSIONS
These findings suggest that the enzymatic properties of human and cynomolgus monkey UGT1A1 enzymes are very similar.
Hanioka
Nobumitsu
N
Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima-naka, Kita-ku, Okayama, Japan. hanioka@pharm.okayama-u.ac.jp
Tanabe
Natsuko
N
Jinno
Hideto
H
Tanaka-Kagawa
Toshiko
T
Nagaoka
Kenjiro
K
Naito
Shinsaku
S
Koeda
Akiko
A
Narimatsu
Shizuo
S
D000595:Amino Acid Sequence; D000818:Animals; D002166:Camptothecin / Q000031:analogs & derivatives / Q000378:metabolism; D003374:Coumarins / Q000378:metabolism; D004958:Estradiol / Q000378:metabolism; D015870:Gene Expression; D014453:Glucuronosyltransferase / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D000077146:Irinotecan; D008252:Macaca fascicularis / Q000378:metabolism*; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D000099148:UGT1A1 Enzyme
D002166:Camptothecin; D003374:Coumarins; D004958:Estradiol; D014453:Glucuronosyltransferase; D000077146:Irinotecan; D011994:Recombinant Proteins; D000099148:UGT1A1 Enzyme; C084236:7-hydroxy-4-trifluoromethylcoumarin