期刊
DRUG METABOLISM AND DISPOSITION
卷 31, 期 1, 页码 133-139出版社
AMER SOC PHARMACOLOGY EXPERIMENTAL THERAPEUTICS
DOI: 10.1124/dmd.31.1.133
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资金
- NATIONAL CENTER FOR RESEARCH RESOURCES [M01RR000054, K01RR000104] Funding Source: NIH RePORTER
- NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES [R01DK058496] Funding Source: NIH RePORTER
- NATIONAL INSTITUTE OF GENERAL MEDICAL SCIENCES [R01GM061834] Funding Source: NIH RePORTER
- NATIONAL INSTITUTE OF MENTAL HEALTH [R01MH058435] Funding Source: NIH RePORTER
- NATIONAL INSTITUTE ON AGING [R01AG017880] Funding Source: NIH RePORTER
- NATIONAL INSTITUTE ON DRUG ABUSE [R21DA013209, R01DA013834] Funding Source: NIH RePORTER
- NCRR NIH HHS [RR-00104, RR-00054] Funding Source: Medline
- NIA NIH HHS [AG-17880] Funding Source: Medline
- NIDA NIH HHS [DA-13834, DA-05258, DA-13209] Funding Source: Medline
- NIDDK NIH HHS [DK-58496] Funding Source: Medline
- NIGMS NIH HHS [GM-61834] Funding Source: Medline
- NIMH NIH HHS [MH-58435] Funding Source: Medline
Investigation of human UDP-glucuronosyltransferase (UGT) isoforms has been limited by a lack of specific substrate probes. In this study serotonin was evaluated for use as a probe substrate for human UGT1A6 using recombinant human UGTs and tissue microsomes. Of the 10 commercially available recombinant UGT isoforms, only UGT1A6 catalyzed serotonin glucuronidation. Serotonin- UGT activity at 40 mM serotonin concentration varied more than 40-fold among human livers (n = 54), ranging from 0.77 to 32.9 nmol/min/mg of protein with a median activity of 7.1 nmol/min/mg of protein. Serotonin- UGT activity kinetics of representative human liver microsomes (n = 7) and pooled human kidney, intestinal and lung microsomes and recombinant human UGT1A6 typically followed one enzyme Michaelis-Menten kinetics. Serotonin glucuronidation activity in these human liver microsomes had widely varying V-max values ranging from 0.62 to 51.3 nmol/min/mg of protein but very similar apparent K-m values ranging from 5.2 to 8.8 mM. Pooled human kidney, intestine, and lung microsomes had V-max values (mean +/- standard error of the estimates) of 8.8 +/- 0.4, 0.22 +/- 0.00, and 0.03 +/- 0.00 nmol/min/mg of protein (respectively) and apparent K-m values of 6.5 +/- 0.9, 12.4 +/- 2.0, and 4.9 +/- 3.3 mM (respectively). In comparison, recombinant UGT1A6 had a V-max of 4.5 +/- 0.1 nmol/min/mg of protein and an apparent K-m of 5.0 +/- 0.4 mM. A highly significant correlation was found between immunoreactive UGT1A6 protein content and serotonin-UGT activity measured at 4 mM serotonin concentration in human liver microsomes (R-s = 0.769; P < 0.001) (n = 52). In conclusion, these results indicate that serotonin is a highly selective in vitro probe substrate for human UGT1A6.
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