Molecular Cloning of the Baboon UDP-Glucuronosyltransferase 2B Gene Family and Their Activity in Conjugating Morphine

Abstract

ABSTRACT:Glucuronidation by UDP-glucuronyltransferase 2B enzymes (UGT2Bs) is a major pathway for the elimination of endobiotics and xenobiotics, including therapeutic drugs. Morphine, a probe drug for UGT2B7, is metabolized to morphine-3-␤-glucuronide (M3G) and morphine-6-␤-glucuronide (M6G) in humans. Morphine has been used in a series of experiments in the baboon to characterize developmental changes in fetal glucuronidation. This study identifies the baboon UGT2B family of enzymes, compares them with that of the human and the monkey (Macaca fascicularis), and measures the activity of the individual baboon UGT2Bs toward morphine. UGT2B cDNAs were cloned from the liver of adult and newborn baboons and expressed in human embryonic kidney 293 cells. The UGT activity toward morphine was assessed by the rate of formation of M3G and M6G by high-performance liquid chromatography. Eight baboon UGT2Bs were cloned and identified: UGT2B41 and UGT2B42, which are 90% homologous to human UGT2B4; UGT2B43, which is 93% homologous to human UGT2B15; and UGT2B39, UGT2B40, UGT2B44, UGT2B45, and UGT2B46, which are 89 to 91% homologous to human UGT2B7. Homology between baboon and monkey UGT2B ranged from 92.6 to 99.1%, with the primary protein structure of UGT2B43 being 99.1% identical to monkey UGT2B20, including a unique R96I substitution. Gene conversion interfered with the phylogenetic signal in the baboon UGT2B7-like and the monkey UGT2B4-like groups and led to concerted evolution of these enzymes. All of the baboon UGT2Bs metabolized morphine to both M3G and M6G. This study lays the foundation for investigating the regulation of UGT2B enzymes during fetal and neonatal development in the baboon.

The UDP-glucuronosyltransferases of the blood-brain barrier: their role in drug metabolism and detoxication

“…The authors suggested that morphine glucuronides found in the CSF after morphine administration was in part formed in situ. As indicated before, among the UGT isoforms expressed in brain, UGT2B7 has been reported to glucuronidate morphine in several animal species and in humans (Court et al, 2003 ; Stone et al, 2003 ; Wong et al, 2006 ; Abildskov et al, 2010 ; Figure 2 ). Although UGT2B7 supported metabolism in liver is well described, the contribution of this UGT isoform in brain is still poorly documented and remains to be investigated in terms of pharmacological effects and potential consequences on brain homeostasis.…”

Predicting and Understanding the Human Microbiome’s Impact on Pharmacology

“…One such drug, morphine, is inactivated by glucuronidation to either morphine 3-glucuronide which has no physiological effect or morphine 6-glucuronide which is ten times more potent than the parent compound [37]. Pharmacogenomics studies have identified several polymorphisms that associate with altered metabolite concentrations [38], including SNPs in the UDP glucuronosyltransferase family 2 which cause differing production of the two metabolites [39]. Both glucuronidated metabolites are excreted into the bile by active transporters, where they travel to the large intestine and are accessed by the gut microbiome.…”

Nanocrystalization: An Emerging Technology to Enhance the Bioavailability of Poorly Soluble Drugs

“…Conventional treatment and some novel carrier system have the disadvantage of stability efficacy, bioavailability and toxicity; therefore, some of the drugs are formulated in the NCs l form and commercialized for effective treatment. Some of the Marketed NCs and their method of preparation are summarized in Table 2 [93][94][95][96][97][98][99][100][101][102][103][104][105][106][107][108].…”