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PubMed1986

Inhibition of the preovulatory prolactin surge in the rat by catechol estrogens: functional and temporal specificity.

Catechol estrogens, administered iv to cycling rats on the morning of proestrus, were able to block the preovulatory PRL surge on the afternoon of the same day. Only catechol estrogens with a low affinity for the estrogen receptor, such as 2-hydroxyestrone and 2-hydroxyestradiol-17 alpha were effective in this respect, while the estrogenic catechol estrogen 2-hydroxyestradiol was unable to influence the PRL surge. The effectiveness of the PRL surge abolition was highly dependent on the state of the endogenous estradiol levels at the time of administration. Only doses given just before the peak secretion of estradiol were effective in blocking the PRL surge. Despite similarities in the inhibition of the preovulatory LH and PRL surges by catechol estrogens, these are considered to occur by different mechanisms because the LH secretion is blocked by all catechol estrogens, while the PRL surge is affected only by catechol estrogens with no estrogen agonist properties. The catechol estrogen blockade of the PRL surge may have physiological parallels and provides a useful probe of the mechanisms of the estrogen-PRL axis.

Animals↗
PubMed1975

Catechol estrogen formation in the central nervous system of the rat.

Conversion of estradiol and estrone to catechol estrogens by rat hypothalamic tissue but not by the cerebral cortex was demonstrated from the incubation of these tissues with estradiol-2-3H and estrone-2-3H and monitoring the incorporation of tritium into water. Direct evidence for this transformation was obtained by isolating the labelled phenazine derivative of 2-hydroxyestrone after hypothalamic incubation with estrone-4-14C.

Animals↗
PubMed1999

UGT2B23, a novel uridine diphosphate-glucuronosyltransferase enzyme expressed in steroid target tissues that conjugates androgen and estrogen metabolites.

Glucuronidation is widely accepted as a mechanism involved in the catabolism and elimination of steroid hormones from the body. However, relatively little is known about the enzymes involved, their specificity for the different steroids, and their site of expression and action. To characterize the pathway of steroid glucuronidation, a novel uridine diphosphate glucuronosyltransferase (UGT) enzyme was cloned and characterized. A 1768-bp complementary DNA, encoding UGT2B23 was isolated from a monkey liver library. Stable expression of UGT2B23 in human HK293 cells and Western blot analysis demonstrated the presence of a 51-kDa protein. The UGT2B23 transferase activity was tested with 62 potential endogenous substrates and was demonstrated to be active on 6 steroids and the bile acid, hyodeoxycholic acid. Kinetic analysis yielded apparent Michaelis constant (Km) values of 0.9, 13.5, 1.6, and 5.7 microM for the conjugation of androsterone (ADT), 3alpha-Diol, estriol, and 4-hydroxyestrone, respectively. RT-PCR analysis revealed that UGT2B23 transcript is expressed in several tissues, including the prostate, mammary gland, epididymis, testis, and ovary. Primary structure analysis shows that UGT2B23 is in the same family of enzymes as the previously characterized monkey isoforms UGT2B9 and UGT2B18, which are active on hydroxyandrogens. The characterization of UGT2B23 as a functional enzyme active on 3alpha-hydroxysteroids, and its expression in extrahepatic tissues, indicate that it may potentially play an important role in estrogen and androgen catabolism in peripheral steroid target tissues.

Amino Acid Sequence↗
PubMed1999

The monkey and human uridine diphosphate-glucuronosyltransferase UGT1A9, expressed in steroid target tissues, are estrogen-conjugating enzymes.

Considering the physiologic importance of the steroid response, which is regulated in part by steroid levels in a given tissue, relatively little is known about steroid glucuronidation, which is widely accepted as a major pathway involved in the catabolism and elimination of steroid hormones from the human body. In a previous study, it was ascertained that the monkey may be the most appropriate model in which to examine the role of steroid glucuronidation. Northern blot analysis of simian RNA, hybridized with human UGT complementary DNA (cDNA) probes demonstrate the similarity of the transcripts. The simian UGT1A09 cDNA isolated from a liver library is 2396 bp and contains an open reading frame encoding 530 amino acids. The predicted primary structure is most homologous to the human UGT1A9 (hUGT1A9) enzyme, which share 93% identity. Stable transfection of the monkey UGT1A09 (monUGT1A09) cDNA into HK293 cells, expresses a microsomal protein with an apparent molecular mass of 55 kDa. Of the more than 30 endogenous substrates tested, both proteins show the highest activity on 4-hydroxyestradiol and 4-hydroxyestrone, followed by 2-hydroxyestradiol and estradiol. RT-PCR analysis demonstrate that UGT1A9 transcript is expressed in several tissues, which include the prostate, testis, breast, ovary, and skin of the monkey and humans. The expression of UGT1A9 in extrahepatic estrogen-responsive tissues, and its high activity on estrogens is consistent with this enzyme having a role in estrogen metabolism.

Amino Acid Sequence↗
PubMed1975

Influence of body weight on estradiol metabolism in young women.

The metabolism of estradiol in girls with anorexia nervosa was compared with obese subjects and normal weight, age and sex matched controls. Increasing body weight was accompanied by a sharp decrease in 2-hydroxylation of estradiol and an increase in 16alpha-hydroxylation. These metabolic changes are discussed in terms of the biological activity of 2-hydroxyestrone and estriol.

Adolescent↗
PubMed1976

Catechol estrogen formation by the human fetal brain and pituitary.

Homogenates of central neuroendocrine tissues from 2 male and 1 female midtrimester fetuses were incubated with (23H) estradiol-17beta. Metabolism at the C-2 position was monitored by measuring the tritium incorporated into water in the incubate. Liberation of tritium from the substrate by hypothalamus, limbic tissues, parietal cortex and pituitary occurred to the extent of 5.1-12.7%, 1.6-8.5%, 4.7-10.8%, and 0.9-4.1% of starting radioactivity, respectively. The nature of the product was confirmed by the isolation of 14C labelled 2-hydroxyestrone derivative from separate incubations with 14C-estrone as the substrate. With or without correction for weight of tissue incubated, catechol estrogen formation under these conditions occurs at levels similar to those seen in rat brain homogenates except that in contrast to the rat, the human cortex is also highly active.

Brain↗
PubMed1976

7beta,17alpha-Dimethyltestosterone (calusterone)-induced changes in the metabolism, production rate, and excretion of estrogens in women with breast cancer: a possible mechanism of action.

The metabolism of estradiol, its production rate and the urinary excretion rate of its metabolites were studied in 5 women patients with breast cancer, 2 of whom were postmenopausal and 3 were ovariectomized, both before and after a period of 7beta,17alpha-dimethyltestosterone (calusterone) therapy. In all cases calusterone caused a profound decrease in the transformation to estriol and an increase in the formation of estrone and 2-hydroxyestrone. The production rate of estrogens was diminished by calusterone in the three overiectomized patients but not in the postmenopausal subjects. The possible participation of the above changes in the chemotherapeutic action of calusterone is discussed.

Adult↗
PubMed1979

Effect of flutamide on estradiol metabolism.

The effect of flutamide, a potent nonsteroidal antiandrogen, on the metabolism of iv tracers of [3H]estradiol was studied in five patients with advanced prostate cancer. The drug produced no change in the percentage of the injected radioactivity recovered in urine or in the glucuronide or nonglucuronide conjugate fractions. Of the five individual metabolites that were quantitated, estrone, estradiol, and estriol were unaffected by flutamide, but the drug caused striking decreases in conversion of estradiol to 2-hydroxyestrone (4.0% vs. 7.4%) (P less than 0.005) and 2-methoxyestrone (1.1% vs. 2.6%; P less than 0.05); every one of the patients showed a marked fall in recovery of both of these compounds. This depression of the formation of 2-oxygenated metabolites is reminiscent of the findings in liver disease; the same abnormality occurs regularly in cirrhosis and frequently in extrahepatic biliary obstruction. Taken together with our previous studies of the effects of flutamide on testosterone and cortisol metabolism, this study demonstrates that flutamide produces multiple functional, reversible, cirrhosis-like disturbances of steroid metabolism. Because these disturbances are universal in the patients studied regardless of whether they had clinical responses to flutamide, we doubt that the steroid metabolic changes play a role in the therapeutic effect of the drug.

Anilides↗
PubMed1981

Effects of catechol estrogen infusions upon gonadotropin and prolactin concentrations in men.

To study the effects of catechol estrogens upon gonadotropin secretion, 2-hydroxyestrone (2-OHE1) and 2-hydroxyestradiol (2-OHE2) were administered iv to young adult men in a range of doses for 4 days. Blood samples were obtained for plasma LH, FSH, and PRL at 20-min intervals for 6 h before and at the end of the infusion period. 2-OHE1 had no effect upon gonadotropins or PRL in doses up to 1.6 mg/day; at 3.2 and 6.6 mg/day, it produced a slight suppression of LH and FSH, with no change in PRL. 2-OHE2 was generally ineffective at 100 micrograms/day, but doses from 200-800 micrograms/day suppressed gonadotropins, without changes in PRL. These infusions elevated 2-OHE1 and 2-OHE2 plasma levels to values comparable to those measured in late pregnancy. There were no associated effects upon blood pressure and only minimal changes in urinary catecholamine excretion. No effects that could be interpreted as antiestrogenic were observed. These results are consistent with the hypothesis that circulating catechol estrogens behave as weak estrogens in men.

Adult↗
PubMed1987

Increased aromatase activity in pubic skin fibroblasts from patients with isolated gynecomastia.

Aromatase activity (AR) was studied in pubic skin fibroblasts from eight patients with isolated gynecomastia (PSFG) and five normal subjects (PSFC). Cell monolayers were incubated in the presence of [3H]androstenedione (2 nM) for 4 or 24 h. Culture medium was extracted after addition of [14C] carriers to monitor recovery. Metabolites were separated by two successive chromatographic steps. Estrone (E1) and estradiol (E2) were characterized by crystallization, the other metabolites: 16-hydroxyestrone (16 alpha-OHE1) estriol (E3), and epiestriol (epiE3) by their chromatographic migration. AR was expressed either as femtomoles of E2 per microgram DNA (ARE2) or as total aromatized metabolites (ART = E1 + E2 + 16 alpha-OHE1 + E3 + epiE3/microgram DNA). After 4 h of incubation, no ARE2 could be measured in PSFC; it was low but significant in PSFG (0.03 +/- 0.02 (SEM) fmol/microgram DNA, P less than 0.01). The difference in ART was even more striking: 0.28 +/- 0.1 fmol/microgram DNA in PSFC, 3.15 +/- 2.88 in PSFG (P less than 0.05). 16 alpha-OHE1 represented in this latter group 62.5% of total aromatized metabolites vs. 39% in PSFC. After 24 h, ART was 4.17 +/- 3.70 and 1.02 +/- 0.42 fmol/microgram DNA in PSFG and PSFC, respectively (P less than 0.05); E3 + epiE3 represented 50% of the metabolites in both groups. In conclusion, AR is increased in PSFG relative to PSFC and an important oxidative metabolism of estrogens exists in both types of cells. This increased peripheral AR could result in increased formation of estrogens at the target cell site and represent an element of androgen-estrogen imbalance which would favor the development of gynecomastia.

Adolescent↗
PubMed1987

The effect of a low fat diet on estrogen metabolism.

Women who consume a diet low in fat are at lower risk for breast cancer than women whose diet is relatively high in fat. To investigate the effects of a low fat diet on estrogen metabolism, six normal young women were studied while eating a Western-style high fat diet and again after 2 months of consuming a defined low fat diet. Both studies involved the simultaneous administration of [3H]estradiol [( 3H]E2) orally and [14C]E2 iv and the subsequent collection of multiple blood samples and urine for 96 h. The blood samples were analyzed for radioactivity as estrone (E1), E2, their glucuronides, and E1 sulfate. An aliquot of the pooled 96-h urine was analyzed for radioactivity as the glucuronides and sulfates of E1, E2, estriol, 16 alpha-hydroxyestrone (16 alpha-OHE1), and the catechol estrogens, i.e. 2-hydroxy and 2-methoxy metabolites of E1 and E2. The low fat diet resulted in a consistent and significant (P less than 0.05) decrease in urinary excretion of both 16-hydroxylated metabolites, estriol and 16 alpha-OHE1, expressed as a percentage of administered dose of [3H]E2 and [14C]E2, and an increase in the excretion of the catechol estrogens. These changes in metabolite excretion were not, however, mirrored by changes in the MCRs or conversion ratios of either [3H]E2 or [14C]E2. Thus, while neither the clearance of E2 from the blood nor its absorption from the intestinal tract was altered by a relatively short term decrease in dietary fat, there was a shift in the pattern of urinary metabolites away from the purported carcinogenic estrogen (16 alpha-OHE1) and toward the less active catechol estrogens. This may represent an important mechanism whereby low fat diets decrease the risk of breast cancer.

Adult↗
PubMed1993

Magnetic resonance imaging of overall and regional body fat, estrogen metabolism, and ovulation of athletes compared to controls.

The association of menstrual dysfunction of athletes with changes in body composition has been controversial, because most estimations of body fatness have been indirect. Using magnetic resonance imaging, we quantified the sc and internal fat over a specific volume from the fifth thoracic vertebra to femoral fat in the upper thigh and at 4 other anatomical landmarks of 17 athletes (13 oarswomen and 4 runners) compared to that in 11 nonathletic controls. The magnetic resonance imaging data were also analyzed for the athletes and controls in relation to ovulatory status, which was determined by assay of urinary pregnanediol glucuronide, and in relation to the extent of 2-hydroxylation of estradiol to a nonpotent metabolite, 2-hydroxyestrone, which was evaluated by radiometric analysis. We found that 1) the relative and absolute body fat values of the athletes were significantly less (P < 0.05) than those of the controls overall and at each of the six regional sites, although the body weights of the rowers were significantly heavier than those of the controls, and the runners did not differ from the controls; 2) the ratio of sc fat to internal fat was 80%:20% among both athletes and controls, even though the athletes had significantly less fat; 3) the extent of estradiol 2-hydroxylation was significantly (P = 0.005) inversely related to total fat as a percentage of the total volume and to sc fat as a percentage of the total volume (P = 0.004) overall and at each of the regional fat depots; 4) athletes with menstrual disorders had significantly decreased sc and internal fat overall and at all regional sites compared to controls; and 5) a subgroup of ovulatory rowers had an apparent increase or lack of decrease in internal fat at the level of vertebrae lumbar 4, sacral 1, and sacral 4, compared to controls, whereas their sc fat was decreased at these sites compared to that in controls. Changes in regional fat deposits of both sc and internal fat may be involved in the menstrual dysfunction of the athletes in addition to their decreased overall fatness. The body weight and body mass index of well trained athletes can be a misleading index of body composition.

Adipose Tissue↗
PubMed1982

Estradiol 17 beta-sulfate as a substrate for 2-hydroxylation enzyme of rat liver microsomes (clinical analysis on steroids. XX).

4-14C-Estradiol and its 17 beta-sulfate were incubated with rat liver microsomes under NADPH-generating system. Estradiol in liver microsomes from male and female rats was metabolized to multiple kinds of oxidized products including estrone, 2-hydroxyestrone, 2-hydroxyestradiol, and other minor steroids. Incubation of estradiol 17 beta-sulfate was carried out by the same condition, and it was shown that the metabolic pattern between male and female rats was different. By incubation of estradiol 17 beta-sulfate with male rat liver microsomes, 2-hydroxyestradiol 17 beta-sulfate was obtained as the sole product (6%). The hydroxylation was shown to occur without cleavage of the conjugate group. No such regulating effect by conjugate group on 2-hydroxylation of estradiol 17 beta-sulfate was observed in liver microsomes from female rats. The amount of 2-hydroxyestradiol 17 beta-sulfate formed was only 1%, and other metabolites which were thought to be monohydroxylated estradiols were produced as the major products. The 2-hydroxylated metabolite of estradiol 17 beta-sulfate was confirmed by its isolation as a stable form of derivative by the following way. The incubation mixture of massive amount of estradiol 17 beta-sulfate was extracted with n-butanol. Methylation of the extract with diazomethane, followed by acid-catalized hydrolysis, acetylation, and finally separation by preparative thin-layer chromatography, gave a crystalline material, the spectral properties of which were completely identical with those of the synthetic specimen, 2, 3-dimethoxy-1,3,5(10)-estratrien-17 beta-yl acetate.

Animals↗
PubMed2000

The oxidative metabolism of estradiol conditions postmenopausal bone density and bone loss.

Because lifelong exposure to estrogen is a strong determinant of bone mass, we asked whether metabolic conversion of estrogen to either inactive or active metabolites would reflect postmenopausal bone mineral density (BMD) and rate of bone loss. Biochemical markers of inactive estrogen metabolites, urinary 2-hydroxyestrogen (2OHE1) and 2-methoxyestrogen (2MeOE1), and active metabolites, urinary 16alpha-hydroxyestrone (16alphaOHE1), estradiol (E2), and estriol (E3), were determined in 71 untreated, healthy postmenopausal women (age, 47-59 years) followed prospectively for 1 year. Urinary 2MeOE1 was correlated negatively with baseline vertebral (anteroposterior [AP] projection, r = -0.23 andp < 0.05; lateral view, r = -0.27 and p < 0.05) and proximal femur bone density measured by dual-energy X-ray absorptiometry (DXA; total, r = -0.38 and p < 0.01; neck, r = -0.28 and p = 0.02; trochanter, r = -0.44 and p < 0.01). BMDs of women in the lowest quartile of urinary 2MeOE1 (< 15 ng/g) were significantly higher than those in the highest quartile at all skeletal sites (p < 0.05). Likewise, women in the lowest quartile of urinary 2OHE1/16alphaOHE1 ratio (< 1.6) did not experience bone loss after 1 year, in contrast to women in the higher quartiles. We propose that the rate of inactivation of estrogens through 2-hydroxylation may contribute to postmenopausal osteoporosis.

Absorptiometry, Photon↗
PubMed1980

Studies on the involvement of lysosomes in estrogen action, III. The dehydrogenation of estradiol to estrone by porcine endometrial lysosomes.

Endometrial cells from prepuberal pigs contain an estradiol 17 beta-dehydrogenase. By differential centrifugation of homogenate fractions and isopycnic separation of the particles sedimenting in the 600 leads to 38000 x g range, accompanied by marker enzyme and electron microscopic analyses, the enzyme appears to be exclusively associated with a subpopulation of lysosomes. It displays a high affinity for estradiol with a Km = 5 x 10(-7) mol/l. Dehydrogenation of estradiol to estrone is favorably driven by NAD, poorly by NADP. The reverse reaction with estrone as substrate and either NADH or NADPH or NADPH + regenerating system as cosubstrate does not proceed beyond the detection level, but trace amounts of 6 alpha/7 alpha-hydroxyestrone are observed at pH 6.5 with the latter two cosubstrates.

Animals↗
PubMed1998

UDPGT cDNA expression and UDPGT1 in human liver.

Following expression of UDPGTh1 and UDPGTh2 in Cos-1 cells, each isoform metabolized three types of dihydroxy- or trihydroxy-substituted ring structures, including the 3,4-catechol estrogen (4-hydroxyestrone), estriol and 17-epiestriol, and hyodeoxycholic acid (HDCA), but the UDPGTh2 isozyme was 100-fold more efficient than UDPGTh1. UDPGTh1 and UDPGTh2 are 86% identical overall (76 differences out of 528 amino acids), including 55 differences in the first 300 amino acids of the amino terminus, a domain which confers isoform substrate specificity. The data indicate a high level of conservation in the amino terminus is not required for the preservation of substrate specificity. Analysis of glucuronidation activity encoded by UDPGTh1/UDPGTh2 chimeric cDNAs constructed at their common restriction sites, Sac I (codon 279), Nco I (codon 385), and Hha I (codon 469), showed that nine amino acids between residues 385 and 469 are important for catalytic efficiency, suggesting that this region represents a domain which is critical for catalysis but distinct from that responsible for aglycon selection. Screening of leukocyte DNA cosmid library with human UDPGT-Br1 (1-470 bps) or UDPGT-Br2 (1-450 bps) resulted in three overlapping clones, which were isolated and mapped by endonucleases. Construction of subclones and DNA sequencing, Southern blot analysis revealed that a cluster of 4 exons (132, 88, 220, 1032 bps in one clone) encodes the entire region of 3' identity shared between human UDPGT-phenol, human UDPGT-Br1 and human UDPGT-Br2. A similar strategy but using probes which correspond to the unique regions of human UDPGT-Br1 and human UDPGT-Br2 showed that the exon 1 of UGT1A and UGT1D encodes the unique region of human UDPGT-Br1, and human UDPGT-Br2 and is located 5.6 and 49 Kb, respectively, upstream of the 4 common exons.

Glucuronosyltransferase↗
PubMed1991

Oestrogen-induced enhancement of myeloperoxidase activity in human polymorphonuclear leukocytes--a possible cause of oxidative stress in inflammatory cells.

Micromolar concentrations of beta-estradiol, estrone, 16-alpha-hydroxyestrone and estriol enhance the oxidative metabolism of activated human PMNL's. The corresponding 2-hydroxylated estrogens 2-OH-estradiol, 2-OH-estrone and 2-OH-estriol act on the contrary as powerful inhibitors of cell activity. Equilenine, a naturally occurring steroid hormone structurally closely related to estrone, removes the estrogen-induced increase in oxidative metabolism of activated PMNL's without diminishing cell activity determined in the absence of enhancing hormone. A number of other female and male sexual hormones were without potentiating effect. The cell response to hormone treatment was assayed as increase (or decrease) in LU-dependent CL of activated PMNL's. When assaying LUC-dependent CL of the cells no stimulatory effects of the estrogens could be detected. This fact may imply that the myeloperoxidase enzyme system of the cells is the target for the hormonal action. Various inhibition experiments using activated PMNL's or purified MPO confirmed this conclusion. The efficicious hormones induced approximately a doubling of CL of activated cells and a tenfold increase of the activity of purified MPO. If cell activity was initiated by the additions of low concentrations of hydrogen peroxide, the presence of estrogens caused a remarkable enhancement of the luminol-dependent chemiluminescence. PMNL's activated with fMLP release MPO activity into the surrounding cell medium. It has been found here that the presence of estrogens in micromolar concentrations greatly increases such enzyme release. Release of MPO activity from the cells could be achieved by the mere addition of estrogenic hormones. Estrogen-induced release of enzyme activity was abrogated by the simultaneous presence of equilenine in the cell suspension. Released enzyme responded vigorously to estrogens in the presence of chloride ions and its substrate, hydrogen peroxide. About a tenfold increase in enzyme activity could be measured in the presence of 5 microM beta-estradiol or esteriol. The activity of the released enzyme (as well of purified MPO) was effectively inhibited by small amounts of anti-MPO antibodies. This observation together with other inhibition experiments was taken as evidence for the view that the released enzyme was identical with myeloperoxidase.

Equilenin↗
PubMed1999

Characterization and substrate specificity of UGT2B4 (E458): a UDP-glucuronosyltransferase encoded by a polymorphic gene.

Variations in glucuronidation activities among different individuals have been reported; however, genetic polymorphisms in the genes encoding phase II drug metabolizing UDP-glucuronosyltransferases have not been studied extensively. A novel UGT2B cDNA clone UGT2B4(E458) was isolated from human prostate and LNCaP cell cDNA libraries. The cDNA encoding UGT2B4(E458) is 2097 bp in length and has an open reading frame of 1584 nucleotides encoding a protein of 528 amino acids. Characterization of the UGT2B4(E458) cDNA revealed nucleotide differences with the previously published UGT2B4 and UGT2B11 cDNAs. These variations in the UGT2B4 sequence lead to an amino acid change from aspartic acid to glutamic acid at position 458. In the previous UGT2B11 cDNA (which has subsequently been renamed UGT2B4 (L109,396, D458)), leucine residues are found at positions 109 and 396, whereas phenylalanines are present at these positions in the UGT2B4(D458) and UGT2B4(E458) enzymes. Analysing the genomic DNA of 26 unrelated Caucasian individuals demonstrated the presence of variant alleles encoding UGT2B4(D458) and UGT2B4(E458). Stable expression of UGT2B4(E458) cDNA in HK293 cells demonstrates the presence of a 52 kDa protein, which is in agreement with other characterized (UGT2B proteins. UGT2B4(E458) conjugates hyodeoxycholic acid (HDCA) as well as 4-hydroxyestrone (4-OH-E1), androstane-3alpha,17beta-diol (3alpha-diol) and androsterone (ADT). Specific reverse transcriptase-polymerase chain reaction analysis revealed expression of UGT2B4(D458) and UGT2B4(E458) transcripts in a wide range of extrahepatic tissues, including the liver, kidney, testis, mammary gland, prostate, placenta, adipose, adrenal, skin and lung. Our results suggest that UGT2B4(E458) and UGT2B(E458) are two widely expressed isoenzymes, and that polymorphism in the UGT2B4 gene might be responsible for differences in UGT2B4 enzymatic properties.

Base Sequence↗