Racemization of the substrate and product by serine palmitoyltransferase from Sphingobacterium multivorum yields two enantiomers of the product from d-serine.

Serine palmitoyltransferase (SPT) catalyzes the pyridoxal-5'-phosphate (PLP)-dependent decarboxylative condensation of l-serine and palmitoyl-CoA to form 3-ketodihydrosphingosine (KDS). Although SPT was shown to synthesize corresponding products from amino acids other than l-serine, it is still arguable whether SPT catalyzes the reaction with d-serine, which is a question of biological importance. Using high substrate and enzyme concentrations, KDS was detected after the incubation of SPT from Sphingobacterium multivorum with d-serine and palmitoyl-CoA.

8-Prenylnaringenin tissue distribution and pharmacokinetics in mice and its binding to human serum albumin and cellular uptake in human embryonic kidney cells.

8-Prenylnaringenin (8-PN), a hop flavonoid, is a promising food substance with health benefits. Compared with nonprenylated naringenin, 8-PN exhibits stronger estrogenic activity and prevents muscle atrophy. Moreover, 8-PN prevents hot flushes and bone loss.

Epicatechin gallate and epigallocatechin gallate are potent inhibitors of human arylacetamide deacetylase.

Recently, in addition to carboxylesterases (CESs), we found that arylacetamide deacetylase (AADAC) plays an important role in the metabolism of some clinical drugs. In this study, we screened for food-related natural compounds that could specifically inhibit human AADAC, CES1, or CES2. AADAC, CES1, and CES2 activities in human liver microsomes were measured using phenacetin, fenofibrate, and procaine as specific substrates, respectively.

Pharmacokinetics and metabolism of cinnamic acid derivatives and flavonoids after oral administration of Brazilian green propolis in humans.

Brazilian green propolis (BGP) has chemical compounds from botanical origin that are mainly cinnamic acid derivatives (artepillin C, baccharin, and drupanin) and flavonoids (kaempferide and 6-methoxykaempferide). These compounds are expected to play an important role in the pharmacological activities of BGP. However, there is little known about the pharmacokinetics and metabolism of these compounds after oral administration of BGP.

Hetero-oligomer formation of mouse UDP-glucuronosyltransferase (UGT) 2b1 and 1a1 results in the gain of glucuronidation activity towards morphine, an activity which is absent in homo-oligomers of either UGT.

UDP-Glucuronosyltransferase (UGT, Ugt) is a major drug metabolizing enzyme family involved in the glucuronidation and subsequent elimination of drugs and small lipophilic molecules. UGT forms homo- and hetero-oligomers that enhance or suppress UGT activity. In our previous study, we characterized mouse Ugt1a1 and all the Ugt isoform belonging to the Ugt2b subfamily and revealed that mouse Ugt2b1 and Ugt1a1 cannot metabolize morphine.

Kanechlor 500-mediated changes in serum and hepatic thyroxine levels primarily occur in a transthyretin-unrelated manner.

The effects of Kanechlor-500 (KC500) on the levels of serum total thyroxine (T ) and hepatic T in wild-type C57BL/6 (WT) and its transthyretin (TTR)-deficient (TTR-null) mice were comparatively examined. Four days after a single intraperitoneal injection with KC500 (100 mg/kg body weight), serum total T levels were significantly decreased in both WT and TTR-null mice. The KC500 pretreatment also promoted serum [ I]T clearance in both strains of mice administrated with [ I]T , and the promotion of serum [ I]T clearance in WT mice occurred without inhibition of the [ I]T -TTR complex formation.

Comprehensive Characterization of Mouse UDP-Glucuronosyltransferase (Ugt) Belonging to the Ugt2b Subfamily: Identification of Ugt2b36 as the Predominant Isoform Involved in Morphine Glucuronidation.

UDP-Glucuronosyltransferases (UGTs) are classified into three subfamilies in mice: Ugt1a, 2b, and 2a. In the subfamily, and appear to correspond to human and The mouse is an important animal for its use in investigations, but the substrate specificities of Ugt isoforms belonging to the 2b subfamily in mice remain largely unknown. To address this issue, we characterized the substrate specificity of all isoforms of the Ugt2b subfamily expressed in the mouse liver.

Expression of UGT1A subfamily in rat brain.

UDP-glucuronosyltransferase (UGT) is an enzyme that catalyses a major phase II reaction in drug metabolism. Glucuronidation occurs mainly in the liver, but UGTs are also expressed in extrahepatic tissues, where they play an important role in local metabolism. UGT1A isoforms catalyse the glucuronidation of several drugs, neurotransmitters and neurosteroids that exert pharmacological and physiological effects on the brain.

Mammalian cytochrome P450-dependent metabolism of polychlorinated dibenzo-p-dioxins and coplanar polychlorinated biphenyls.

Polychlorinated dibenzo-p-dioxins (PCDDs) and coplanar polychlorinated biphenyls (PCBs) contribute to dioxin toxicity in humans and wildlife after bioaccumulation through the food chain from the environment. The authors examined human and rat cytochrome P450 (CYP)-dependent metabolism of PCDDs and PCBs. A number of human CYP isoforms belonging to the CYP1 and CYP2 families showed remarkable activities toward low-chlorinated PCDDs.

Alteration of the function of the UDP-glucuronosyltransferase 1A subfamily by cytochrome P450 3A4: different susceptibility for UGT isoforms and UGT1A1/7 variants.

Functional protein-protein interactions between UDP-glucuronosyltransferase (UGT)1A isoforms and cytochrome P450 (CYP)3A4 were studied. To this end, UGT1A-catalyzed glucuronidation was assayed in Sf-9 cells that simultaneously expressed UGT and CYP3A4. In the kinetics of UGT1A6-catalyzed glucuronidation of serotonin, both Michaelis constant (Km) and maximal velocity (Vmax) were increased by CYP3A4.

Avian cytochrome P450 (CYP) 1-3 family genes: isoforms, evolutionary relationships, and mRNA expression in chicken liver.

Cytochrome P450 (CYP) of chicken and other avian species have been studied primarily with microsomes or characterized by cloning and protein expression. However, the overall existing isoforms in avian CYP1-3 families or dominant isoforms in avian xenobiotic metabolism have not yet been elucidated. In this study, we aimed to clarify and classify all of the existing isoforms of CYP1-3 in avian species using available genome assemblies for chicken, zebra finch, and turkey.

Comparison of serotonin glucuronidation activity of UDP-glucuronosyltransferase 1a6a (Ugt1a6a) and Ugt1a6b: evidence for the preferential expression of Ugt1a6a in the mouse brain.

Mouse UDP-glucuronosyltransferase (Ugt) 1a6a and Ugt1a6b share 98% sequence homology, but there have been no reports to date that compare their expression levels or enzymatic activities in serotonin glucuronidation. Thus, we designed specific primers for Ugt1a6a and Ugt1a6b to compare their expression in mouse brain regions and livers. Ugt1a6a was dominantly expressed in mouse brains, especially the hippocampus, while both Ugt1a6a and Ugt1a6b were highly expressed in mouse livers, indicating that there are significant differences in the expression patterns of Ugt1a6a and Ugt1a6b among mouse tissues.

Comparative study on 2,2',4,5,5'-pentachlorobiphenyl-mediated decrease in serum thyroxine level between C57BL/6 and its transthyretin-deficient mice.

The relationships between the changes in the levels of serum total thyroxine (T(4)), serum T(4)-transthyretin (TTR) complex, and accumulation of T(4) in tissues by 2,2',4,5,5'-pentachlorobiphenyl (PentaCB) were examined using wild-type C57BL/6 (WT) and its TTR-deficient (TTR-null) mice. The constitutive level of serum total T(4) was much higher in WT mice than in TTR-null mice. In WT mice 4 days after a single intraperitoneal injection with PentaCB (112 mg/kg), serum total T(4) level was significantly decreased along with a decrease in serum T(4)-TTR complex, and the levels of serum total T(4) in the PentaCB-treated WT mice were almost the same to those in PentaCB-untreated (control) TTR-null mice.

The critical role of amino acid residue at position 117 of mouse UDP-glucuronosyltransfererase 1a6a and 1a6b in resveratrol glucuronidation.

Mouse UDP-glucuronosyltransferase 1a6 (Ugt1a6) contains two functional copies of 1a6a and 1a6b that share high sequence homology (98%). Only 10 amino acids located around the substrate recognition region are different out of 531 total residues. Although Ugt1a6 plays important roles in conjugating phenolic compounds, the functional characteristics of these isozymes are unclear.

Metabolism of the c-Fos/activator protein-1 inhibitor T-5224 by multiple human UDP-glucuronosyltransferase isoforms.

We developed 3-{5-[4-(cyclopentyloxy)-2-hydroxybenzoyl]-2-[(3-hydroxy-1,2-benzisoxazol-6-yl)methoxy]phenyl} propionic acid (T-5224) as a novel inhibitor of the c-Fos/activator protein-1 for rheumatoid arthritis therapy. We predicted the metabolism of T-5224 in humans by using human liver microsomes (HLM), human intestinal microsomes (HIM), recombinant human cytochrome P450 (P450), and UDP-glucuronosyltransferases (UGTs). T-5224 was converted to its acyl O-glucuronide (G2) by UGT1A1 and UGT1A3 and to its hydroxyl O-glucuronide (G3) by several UGTs, but it was not metabolized by the P450s.

Nutritional status affects fluvastatin-induced hepatotoxicity and myopathy in rats.

Rats that consumed a high-fat and high-sucrose diet (HF diet) developed hepatic steatosis. Treatment of HF diet-fed rats with fluvastatin (8 mg/kg) was lethal, followed by an elevation in levels of plasma aspartate aminotransferase and creatine kinase activities and skeletal muscle toxicity. This study was conducted to determine whether nutritional status affects statin-induced adverse effects in rats.

Metabolism of mono- and dichloro-dibenzo-p-dioxins by Phanerochaete chrysosporium cytochromes P450.

The white-rot fungus Phanerochaete chrysosporium possesses biodegradative capabilities of polychlorinated dibenzo-p-dioxins (PCDDs). One hundred twenty yeast clones expressing individual P450s of P. chrysosporum (PcCYPs), generated in our previous efforts, were screened for transformation of dioxin, and 40 positive clones were obtained.

A possible mechanism for the decrease in serum thyroxine level by a 2,3,7,8-tetrachlorodibenzo-p-dioxin-like polychlorinated biphenyl congener, 3,3',4,4',5-pentachlorobiphenyl in mice.

Serum total thyroxine (T(4)) and free T(4) levels were markedly decreased 7 days after treatment with 3,3',4,4',5-pentachlorobiphenyl (CB126) (2.5 mg/kg i.p.

4-Hydroxy-2,2',3,4',5,5',6-heptachlorobiphenyl-mediated decrease in serum thyroxine level in mice occurs through increase in accumulation of thyroxine in the liver.

4-Hydroxy-2,2',3,4',5,5',6-heptachlorobiphenyl (4-OH-CB187) was selected as a major hydroxylated polychlorinated biphenyl metabolite detected from serum of wildlife and humans and was examined for its effect on level of serum thyroid hormone in mice. Four days after treatment of C57BL/6 and DBA/2 mice with 4-OH-CB187 (1.0 mg/kg), the serum total thyroxine (T(4)) and free T(4) levels were decreased in both strains of mice.

Enzymatic properties of cytochrome P450 catalyzing 3'-hydroxylation of naringenin from the white-rot fungus Phanerochaete chrysosporium.

We cloned full-length cDNAs of more than 130 cytochrome P450s (P450s) derived from Phanerochaete chrysosporium, and successfully expressed 70 isoforms using a co-expression system of P. chrysosporium P450 and yeast NADPH-P450 reductase in Saccharomyces cerevisiae. Of these P450s, a microsomal P450 designated as PcCYP65a2 consists of 626 amino acid residues with a molecular mass of 68.

Interactions between human UDP-glucuronosyltransferase (UGT) 2B7 and UGT1A enzymes.

Glucuronidation catalyzed by UDP-glucuronosyltransferase (UGT) enzymes is an important pathway in the metabolism of drugs as well as environmental chemicals. In this study, protein-protein interactions between human UGT2B7 and UGT1As and their effects on the enzymatic activities were investigated using double expression systems in HEK293 cells (UGT2B7/UGT1A1, UGT2B7/UGT1A4, UGT2B7/UGT1A6, and UGT2B7/UGT1A9). Native-PAGE analysis clearly revealed that UGT2B7 forms homo-oligomers.

Quantitative analysis of UDP-glucuronosyltransferase (UGT) 1A and UGT2B expression levels in human livers.

UDP-glucuronosyltransferases (UGTs) catalyze glucuronidation of a variety of xenobiotics and endobiotics. UGTs are divided into two families, UGT1 and UGT2. The purpose of this study was to estimate the absolute expression levels of each UGT isoform in human liver and to evaluate the interindividual variability.

Ontogenic isoform switching of UDP-glucuronosyltransferase family 1 in rat liver.

The liver undergoes dramatic changes in function during development. The development of UDP-glucuronosyltransferase family 1 (UGT1) isoforms was studied in livers from rats at 16-20days of gestation, at days 1, 2, 3, 4, and 7 of infancy, at days 14 and 28 of childhood, and at day 56 of young adulthood. We found developmental stage-specific switching of regulation of the rat UGT1 gene complex.

The configuration of the 17-hydroxy group variably influences the glucuronidation of beta-estradiol and epiestradiol by human UDP-glucuronosyltransferases.

The glucuronidation of 17beta-estradiol (beta-estradiol) and 17alpha-estradiol (epiestradiol) was studied to elucidate how the orientation of the 17-OH group affects conjugation at the 3-OH or the 17-OH of either diastereomer. Recombinant human UDP-glucuronosyltransferases (UGTs) UGT1A1, UGT1A3, UGT1A7, UGT1A8, and UGT1A10 conjugated one or both diastereomers, mainly at the 3-OH. The activity of UGT1A4 was low and unique because it was directed merely toward the 17-OH of both aglycones.

Dapsone induces oxidative stress and impairs antioxidant defenses in rat liver.

Dapsone (DDS) is currently used in the treatment of leprosy, malaria and in infections with Pneumocystis jirovecii and Toxoplasma gondii in AIDS patients. Adverse effects of DDS involve methemoglobinemia and hemolysis and, to a lower extent, liver damage, though the mechanism is poorly characterized. We evaluated the effect of DDS administration to male and female rats (30 mg/kg body wt, twice a day, for 4 days) on liver oxidative stress through assessment of biliary output and liver content of reduced (GSH) and oxidized (GSSG) glutathione, lipid peroxidation, and expression/activities of the main antioxidant enzymes glutathione peroxidase, superoxide dismutase, catalase and glutathione S-transferase.