Prostate cancer with variants in CYP17 and UGT2B17 genes: a meta-analysis

Both CYP17 and UGT2B17 are suggested to be potential risk factors of prostate cancer (PCa). To date, many studies have evaluated the relationship between CYP17 T-34C and UGT2B17 Del polymorphisms and Prostate cancer with conflicting results. Here, we performed comprehensive meta-analyses of over 25 studies, including results from about 17,000 subjects on the association of CYP17 T-34C and UGT2B17 Del polymorphisms with Prostate cancer. Overall, no significant associations between CYP17 T-34C polymorphism and Prostate cancer risk were found for T versus C (P=0.63), TT versus CC (P=0.52), TT+TC versus CC (P=0.40) or TT versus TC+CC (P=0.98), though there was a marginally significant association with the UGT2B17 Del polymorphism under Del/Del versus Ins/Ins +Ins/Del (P=0.05). In an analysis of various subgroups, there were no substantially significant associations with the CYP17 T-34C polymorphism; while there was a significant association for the UGT2B17 Del/Del genotype in a subgroup of men-based controls (P < 0.0001). The current meta-analysis results suggest that the CYP17 T-34C polymorphism may not be associated with Prostate cancer, while the UGT2B17 Del polymorphism may significantly contribute to prostate cancer susceptibility in men. These findings also support the idea that CYP17 has no significant effects on androgen levels, while UGT2B17 does.     

Genome-wide copy-number-variation study identified a susceptibility gene, UGT2B17, for osteoporosis

Osteoporosis, a highly heritable disease, is characterized mainly by low bone-mineral density (BMD), poor bone geometry, and/or osteoporotic fractures (OF). Copy-number variation (CNV) has been shown to be associated with complex human diseases. The contribution of CNV to osteoporosis has not been determined yet. We conducted case-control genome-wide CNV analyses, using the Affymetrix 500K Array Set, in 700 elderly Chinese individuals comprising 350 cases with homogeneous hip OF and 350 matched controls. We constructed a genomic map containing 727 CNV regions in Chinese individuals. We found that CNV 4q13.2 was strongly associated with OF (p = 2.0 × 10⁻⁴, Bonferroni-corrected p = 0.02, odds ratio = 1.73). Validation experiments using PCR and electrophoresis, as well as real-time PCR, further identified a deletion variant of UGT2B17 in CNV 4q13.2. Importantly, the association between CNV of UGT2B17 and OF was successfully replicated in an independent Chinese sample containing 399 cases with hip OF and 400 controls. We further examined this CNV's relevance to major risk factors for OF (i.e., hip BMD and femoral-neck bone geometry) in both Chinese (689 subjects) and white (1000 subjects) samples and found consistently significant results (p = 5.0 × 10⁻⁴ −0.021). Because UGT2B17 encodes an enzyme catabolizing steroid hormones, we measured the concentrations of serum testosterone and estradiol for 236 young Chinese males and assessed their UGT2B17 copy number. Subjects without UGT2B17 had significantly higher concentrations of testosterone and estradiol. Our findings suggest the important contribution of CNV of UGT2B17 to the pathogenesis of osteoporosis.     

UDP-glucuronosyltransferase 2B15 (UGT2B15) and UGT2B17 enzymes are major determinants of the androgen response in prostate cancer LNCaP cells

Uridine diphosphate-glucuronosyltransferase 2 (UGT2)B15 and B17 enzymes conjugate dihydrotestosterone (DHT) and its metabolites androstane-3alpha, 17beta-diol (3alpha-DIOL) and androsterone (ADT). The presence of UGT2B15/B17 in the epithelial cells of the human prostate has been clearly demonstrated, and significant 3alpha-DIOL glucuronide and ADT-glucuronide concentrations have been detected in this tissue. The human androgen-dependent cancer cell line, LNCaP, expresses UGT2B15 and -B17 and is also capable of conjugating androgens. To assess the impact of these two genes in the inactivation of androgens in LNCaP cells, their expression was inhibited using RNA interference. The efficient inhibitory effects of a UGT2B15/B17 small interfering RNA (siRNA) probe was established by the 70% reduction of these UGT mRNA levels, which was further confirmed at the protein levels. The glucuronidation of dihydrotestosterone (DHT), 3alpha-DIOL, and ADT by LNCaP cell homogenates was reduced by more than 75% in UGT2B15/B17 siRNA-transfected LNCaP cells when compared with cells transfected with a non-target probe. In UGT2B15/B17-deficient LNCaP cells, we observe a stronger response to DHT than in control cells, as determined by cell proliferation and expression of eight known androgen-sensitive genes. As expected, the amounts of DHT in cell culture media from control cells were significantly lower than that from UGT2B15/B17 siRNA-treated cells, which was caused by a higher conversion to its corresponding glucuronide derivative. Taken together these data support the idea that UGT2B15 and -B17 are critical enzymes for the local inactivation of androgens and that glucuronidation is a major determinant of androgen action in prostate cells.     

Isolation and characterization of the human UGT2B15 gene, localized within a cluster of UGT2B genes and pseudogenes on chromosome 4

Glucuronidation is a major pathway of androgen metabolism and is catalyzed by UDP-glucuronosyltransferase (UGT) enzymes. UGT2B15 and UGT2B17 are 95% identical in primary structure, and are expressed in steroid target tissues where they conjugate C19 steroids. Despite the similarities, their regulation of expression are different; however, the promoter region and genomic structure of only the UGT2B17 gene have been characterizedX to date. To isolate the UGT2B15 gene and other novel steroid-conjugating UGT2B genes, eight P-1-derived artificial chromosomes (PAC) clones varying in length from 30 kb to 165 kb were isolated. The entire UGT2B15 gene was isolated and characterized from the PAC clone 21598 of 165 kb. The UGT2B15 and UGT2B17 genes are highly conserved, are both composed of six exons spanning approximately 25 kb, have identical exon sizes and have identical exon-intron boundaries. The homology between the two genes extend into the 5'-flanking region, and contain several conserved putative cis-acting elements including Pbx-1, C/EBP, AP-1, Oct-1 and NF/kappaB. However, transfection studies revealed differences in basal promoter activity between the two genes, which correspond to regions containing non-conserved potential elements. The high degree of homology in the 5'-flanking region between the two genes is lost upstream of -1662 in UGT2B15, and suggests a site of genetic recombination involved in duplication of UGT2B genes. Fluorescence in situ hybridization mapped the UGT2B15 gene to chromosome 4q13.3-21.1. The other PAC clones isolated contain exons from the UGT2B4, UGT2B11 and UGT2B17 genes. Five novel exons, which are highly homologous to the exon 1 of known UGT2B genes, were also identified; however, these exons contain premature stop codons and represent the first recognized pseudogenes of the UGT2B family. The localization of highly homologous UGT2B genes and pseudogenes as a cluster on chromosome 4q13 reveals the complex nature of this gene locus, and other novel homologous UGT2B genes encoding steroid conjugating enzymes are likely to be found in this region of the genome.     

Characterization of a common deletion polymorphism of the UGT2B17 gene linked to UGT2B15

Members of the human UDP-glucuronosyltransferase 2B family are located in a cluster on chromosome 4q13 and code for enzymes whose gene products are responsible for the normal catabolism of steroid hormones. Two members of this family, UGT2B15 and UGT2B17, share over 95% sequence identity. However, UGT2B17 exhibits broader substrate specificity due to a single amino acid difference. Using gene-specific primers to explore the genomic organization of these two genes, it was determined that UGT2B17 is absent in some human DNA samples. The gene-specific primers demonstrated the presence or absence of a 150 kb genomic interval spanning the entire UGT2B17 gene, revealing that UGT2B17 is present in the human genome as a deletion polymorphism linked to UGT2B15. Furthermore, it is shown that the UGT2B17 deletion polymorphism shows Mendelian segregation and allele frequencies that differ between African Americans and Caucasians.     

UDP-glucuronosyltransferase 2B17 genotype and the risk of lung cancer among Austrian Caucasians

Background: The enzyme uridine diphospho glucuronosyltansferase 2B17 (UGT2B17) glucuronidates several endogenous and exogenous compounds, including carcinogens from tobacco smoke like 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanl (NNAL). UGT2B17 shows a remarkable copy number variation (CNV) and an association between deletion genotype and increased risk of lung adenocarcinoma in women has been previously reported. Methods: We investigated the UGT2B17 CNV by PCR in 453 Austrian lung cancer patients and in 449 healthy donors and analyzed the impact on lung cancer susceptibility and outcome. Results: Copy numbers of UGT2B17 were 44.4% (+/+), 42.2% (+/?) and 13.5% (?/?) in lung cancer patients and 43.0% (+/+), 46.3% (+/?) and 10.7% (?/?) among healthy donors. The null genotype was not significantly more frequent among women with adenocarcinoma compared to healthy women (p = 0.59). There was no association with overall survival (p = 0.622) and no significant sex-associated (p = 0.423) or histology-related impact on development of lung cancer. Conclusion: UGT2B17 deletion genotype was not associated with a significant risk for lung cancer development or outcome in our Central European patient cohort. Our study indicates that UGT2B17 is not a crucial factor in lung carcinogenesis among Caucasians and shows the importance of investigating such markers in large cohorts from different populations.     

Differential allelic expression of c.1568C > A at UGT2B15 is due to variation in a novel cis-regulatory element in the 3'UTR

Differential allelic expression (DAE) is a powerful tool to identify cis-regulatory elements for gene expression. The UDP-glucuronosyltransferase 2 family, polypeptide B15 (UGT2B15), is an important enzyme involved in the metabolism of multiple endobiotics and xenobiotics. In the present study, we measured the relative expression of two alleles at SNP c.1568C>A (rs4148269) in this gene, which causes an amino acid substitution (T523K). An excess of the C over the A allele was consistently observed in both liver (P = 0.0021) and breast (P = 0.012) samples, suggesting that SNP(s) in strong linkage disequilibrium (LD) with c.1568C>A can regulate UGT2B15 expression in both tissues. By resequencing, one such SNP, c.1761T>C (rs3100) in 3′ untranslated region (UTR), was identified. Reporter gene assays showed that the 1761T allele results in a significantly higher gene expression level than the 1761C allele in HepG2, MCF-7, LNCaP, and Caco-2 cell lines (all P < 0.001), thus indicating that this variation can regulate UGT2B15 gene expression in liver, breast, colon, and prostate tissues. Considering its location, we postulated that this SNP is within an unknown microRNA binding site and can influence microRNA targeting. Considering the importance of UGT2B15 in metabolism, we proposed that this SNP might contribute to multiple cancer risk and variability in drug response.     

The presence of the UGT2B17 gene is associated with lung cancer in male Chinese Han smokers

The genetic impact of UGT2B17 gene copy number variation (CNV) on tobacco-smoking related cancers is of interest since this enzyme plays an important role in glucuronidation of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a major metabolite from the nicotine-derived tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). This is an important mechanism for NNK detoxification. The UGT2B17 gene varies in copy number from zero to two per individual in humans and this CNV was genotyped in 148 lung cancer and 92 control Chinese Han samples by a PCR-based method. The frequency of the UGT2B17 undeleted allele was higher in lung cancer patients than in controls but not significantly so (p = 0.042, OR 1.6; 95% CI: 0.97–2.57); however, in smokers with lung cancer its frequency is significantly higher than in controls, (p = 0.016, OR 1.8; 95% CI: 1.08–3.18). The undeleted allele was also significantly higher in the male lung cancer group (p = 0.015, OR 1.86; 95% CI: 1.09–3.16), and even higher in the male smoker lung cancer group (p = 0.004, OR 2.23; 95% CI: 1.27–3.89). In subsets of the male smoker lung cancer group defined by their histopathology, the undeleted allele was significantly higher in squamous cell carcinoma (p = 0.026, OR 2.09; 95% CI: 1.06–4.10). These results show that UGT2B17 copy number is associated with male smoker lung cancer in China, especially squamous cell carcinoma.     

Meta-Analysis Reveals a Lack of Association between UGT2B17 Deletion Polymorphism and Tumor Susceptibility

Purpose

UGT2B17 is a vital member of the UGT2 family and functions as a detoxification enzyme which catalyzes the glucuronidation of lipophilic compounds. Accumulating evidences implicates that it may contribute to the susceptibility of tumor risk. Identification of a UGT2B17 deletion polymorphism has attracted studies to evaluate the association between the UGT2B17 deletion polymorphism and tumor risk in diverse populations. However, the available results are conflicting.

Methods

A meta-analysis based on 14 studies from 10 publications including 5,732 cases and 5,112 controls was performed. Published literature from PubMed, EMBASE and Web of Science was pooled and the crude odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to estimate the strength of the associations.

Results

Conclusively, our results indicate that individuals with a UGT2B17 deletion polymorphism were associated with tumor risks (OR = 1.29, 95% CI = 1.03–1.63, P<0.001) in a recessive model. However, after excluding two studies for their heterogeneity, the result then demonstrated that the UGT2B17 deletion polymorphism was not associated with tumor risks (OR = 1.118, 95%CI = 0.938–1.332, P>0.1). A subgroup analysis based on tumor type, sex or race did not show significant results.

Conclusion

These results suggest that the UGT2B17 deletion polymorphism is not associated with tumor risks.     

Activators of the farnesoid X receptor negatively regulate androgen glucuronidation in human prostate cancer LNCAP cells

Androgens are major regulators of prostate cell growth and physiology. In the human prostate, androgens are inactivated in the form of hydrophilic glucuronide conjugates. These metabolites are formed by the two human UGT2B15 [UGT (UDP-glucuronosyltransferase) 2B15] and UGT2B17 enzymes. The FXR (farnesoid X receptor) is a bile acid sensor controlling hepatic and/or intestinal cholesterol, lipid and glucose metabolism. In the present study, we report the expression of FXR in normal and cancer prostate epithelial cells, and we demonstrate that its activation by chenodeoxycholic acid or GW4064 negatively interferes with the levels of UGT2B15 and UGT2B17 mRNA and protein in prostate cancer LNCaP cells. FXR activation also causes a drastic reduction of androgen glucuronidation in these cells. These results point out activators of FXR as negative regulators of androgen-conjugating UGT expression in the prostate. Finally, the androgen metabolite androsterone, which is also an activator of FXR, dose-dependently reduces the glucuronidation of androgens catalysed by UGT2B15 and UGT2B17 in an FXR-dependent manner in LNCaP cells. In conclusion, the present study identifies for the first time the activators of FXR as important regulators of androgen metabolism in human prostate cancer cells.     

Steroid 5-alpha-reductase type 2 (SRD5A2) V89L and A49T polymorphisms and sporadic prostate cancer risk: a meta-analysis

Steroid 5-α-reductase type 2 (SRD5A2) V89L and A49T polymorphisms are thought to play a crucial role in the androgen synthesis and metabolic pathway, but their associations with prostate cancer risk remain controversial. To provide a more precise estimation of the associations between V89L and A49T polymorphisms and prostate cancer risk, we performed a meta-analysis using all published case–control studies of prostate cancer since January 1995. We used odds ratio (OR) and its 95 % confidence interval (CI) to assess the strength of the association under various genetic models in both overall and stratified analyses. We also calculated the false-positive report probability, the power of the current study, and the observed P value for significant findings. This analysis included 45 eligible studies of a total of 15,562 cases and 15,385 controls, in which no significant associations were found for the V89L polymorphisms under all genetic models. However, small excess prostate cancer risk was associated with the 49T allele in mixed populations compared with the 49A allele (OR = 1.24, 95 % CI = 1.02–1.50), and similar results were observed in Caucasians (OR = 1.24, 95 % CI = 1.01–1.53). The sensitivity analysis further strengthened the validity of these findings without publication bias. Although there was no overall association between V89L and prostate cancer risk, A49T might play a role in the etiology of prostate cancer among Caucasians. Additional large and well-designed studies are warranted to validate these findings.     

Identification of UGT2B9*2 and UGT2B33 isolated from female rhesus monkey liver

Two UDP-glucuronosyltransferases (UGT2B9(*)2 and UGT2B33) have been isolated from female rhesus monkey liver. Microsomal preparations of the cell lines expressing the UGTs catalyzed the glucuronidation of the general substrate 7-hydroxy-4-(trifluoromethyl)coumarin in addition to selected estrogens (beta-estradiol and estriol) and opioids (morphine, naloxone, and naltrexone). UGT2B9(*)2 displayed highest efficiency for beta-estradiol-17-glucuronide production and did not catalyze the glucuronidation of naltrexone. UGT2B33 displayed highest efficiency for estriol and did not catalyze the glucuronidation of beta-estradiol. UGT2B9(*)2 was found also to catalyze the glucuronidation of 4-hydroxyestrone, 16-epiestriol, and hyodeoxycholic acid, while UGT2B33 was capable of conjugating 4-hydroxyestrone, androsterone, diclofenac, and hyodeoxycholic acid. Three glucocorticoids (cortisone, cortisol, and corticosterone) were not substrates for glucuronidation by liver or kidney microsomes or any expressed UGTs. Our current data suggest the use of beta-estradiol-3-glucuronidation, beta-estradiol-17-glucuronidation, and estriol-17-glucuronidation to assay UGT1A01, UGT2B9(*)2, and UGT2B33 activity in rhesus liver microsomes, respectively.     

基因组拷贝数变异及其突变机理与人类疾病

拷贝数变异(Copy number variation,CNV)是由基因组发生重排而导致的,一般指长度为1 kb以上的基因组大片段的拷贝数增加或者减少,主要表现为亚显微水平的缺失和重复。CNV是基因组结构变异(Structural variation,SV)的重要组成部分。CNV位点的突变率远高于SNP(Single nucleotide polymorphism),是人类疾病的重要致病因素之一。目前,用来进行全基因组范围的CNV研究的方法有:基于芯片的比较基因组杂交技术(array-based comparative genomic hybridization,aCGH)、SNP分型芯片技术和新一代测序技术。CNV的形成机制有多种,并可分为DNA重组和DNA错误复制两大类。CNV可以导致呈孟德尔遗传的单基因病与罕见疾病,同时与复杂疾病也相关。其致病的可能机制有基因剂量效应、基因断裂、基因融合和位置效应等。对CNV的深入研究,可以使我们对人类基因组的构成、个体间的遗传差异、以及遗传致病因素有新的认识。     

Inactivation by UDP-glucuronosyltransferase enzymes: the end of androgen signaling

Conjugation by UDP-Glucuronosyltransferase (UGT) is the major pathway of androgen metabolism and elimination in the human. High concentrations of glucuronide conjugates of androsterone (ADT) and androstane-3alpha,17beta-diol (3alpha-diol) are present in circulation and several studies over the last 30 years have concluded that the serum levels of these metabolites might reflect the androgen metabolism in several tissues, including the liver and androgen target tissues. Three UGT2B enzymes are responsible for the conjugation of DHT and its metabolites ADT and 3alpha-diol: UGT2B7, B15 and B17. UGT2B7 is expressed in the liver and skin whereas UGT2B15 and B17 were found in the liver, prostate and skin. Very specific antibodies against each UGT2B enzyme have been obtained and used for immunohistochemical studies in the human prostate. It was shown that UGT2B17 is expressed in basal cells whereas UGT2B15 is only localized in luminal cells, where it inactivates DHT. By using LNCaP cells, we have also demonstrated that the expression and activity of UGT2B15 and B17 are modulated by several endogenous prostate factors including androgen. Finally, to study the physiological role of UGT2B enzymes, transgenic mice bearing the human UGT2B15 gene were recently obtained. A decrease in reproductive tissue weight from transgenic animals compared to those from control animals was observed. In conclusion, the conjugation by UGT2B7, B15 and B17, which represents a non-reversible step in androgen metabolism, is an important means by which androgens are regulated locally. It is also postulated that UGT enzymes protect the tissue from deleteriously high concentrations of active androgen.     

Prognostic Significance of ESR1 Amplification and ESR1 PvuII,CYP2C19*2, UGT2B15*2 Polymorphisms in Breast Cancer Patients

Introduction

Amplification of the ESR1 gene, coding for estrogen receptor alpha, was shown to predict responsiveness to tamoxifen, however its prognostic impact in breast cancer patients has not been thoroughly investigated. Other factors that could contribute to responsiveness to tamoxifen treatment are polymorphisms in ESR1 gene and genes involved in tamoxifen metabolism.The aim of this study was to assess the prognostic role of ESR1 gene dosage in a consecutive group of breast cancer patients and to correlate this feature with clinico-pathological factors. Additionally, ESR1 PvuII, CYP2C19*2 and UGT2B15*2 polymorphisms were analyzed in the tamoxifen-treated subgroup of patients.

Materials and Methods

Primary tumor samples from 281 stage I-III consecutive breast cancer patients were analyzed for ESR1 gene dosage using real-time PCR with locked nucleic acids hydrolysis probes. In the tamoxifen-treated subgroup of patients, ESR1 PvuII, CYP2C19*2 and UGT2B15*2 polymorphism in leukocytes genomic DNA were analyzed. Results were correlated with clinico-pathological factors and with disease-free survival (DFS) and overall survival (OS).

Results

ESR1 amplification (with a cut-off level of 2.0) was found in 12% of the entire group of breast cancer patients, and in 18% of the ER-negative subgroup. This feature was associated with decreased DFS both in the entire group (P=0.007) and in the ER-negative subgroup (P=0.03), but not in the tamoxifen-treated patients.Patients with ESR1 PvuII wt/wt genotype and at least one UGT2B15 wt allele had a worse DFS (P=0.03) and showed a trend towards decreased Os (P=0.08) in comparison to patients with ESR1 PvuII wt/vt or vt/vt genotype and UGT2B15 *2/*2 genotype.

Conclusions

ESR1 amplification can occur in ER-negative tumors and may carry poor prognosis. In the tamoxifen-treated subgroup, poor prognosis was related to the combined presence of ESR1 PvuII wt/wt and UGT2B15wt/wt or wt/*2 genotype.     

Thymidylate synthase polymorphisms are associated to therapeutic outcome of advanced non-small cell lung cancer patients treated with platinum-based chemotherapy

Thymidylate synthase (TYMS) has three polymorphisms that may modulate thymidylate synthase (TS) expression levels: (1) 28 base pairs (bp) variable number tandem repeat (VNTR) (rs34743033); (2) single nucleotide polymorphism (SNP) C>G at the twelfth nucleotide of the second repeat of 3R allele (rs2853542); and (3) 6 bp sequence deletion (1494del6, rs34489327). This study was conducted to evaluate the influence of TYMS polymorphisms on the survival of Portuguese patients with advanced non-small cell lung cancer (NSCLC) undergoing platinum-based chemotherapy. Our results showed no statistically significant differences between VNTR genotypes; although, considering the SNP C>G, homozygotes 3RG presented a better prognostic at 36 months (p = 0.004) and overall survival (p = 0.003) when compared to 2R3RG patients. Patients with “median/high expression genotypes” demonstrated a better survival at 12 months (p = 0.041) when compared to “low expression genotypes”. Furthermore, 6 bp? carriers (p = 0.006) showed a better survival at 12 months when compared to 6 bp+ homozygotes patients. When analyzing TYMS haplotypes, better survival at 12 months was observed for patients carrying haplotypes with the 6 bp? allele (2R6 bp?; p = 0.026 and 3RG6 bp?; p = 0.045). This is the first report that evaluates the three major TYMS polymorphisms in the therapeutic outcome of NSCLC in Portugal. According to our results, the TYMS polymorphisms may be useful tools to predict which advanced NSCLC patients could benefit more from platinum-based chemotherapy regimens.     

The structural basis of conserved residue variant effect on enzyme activity of UGT2B15

UDP-glucuronosyltransferase 2B15 (UGT2B15) is a crucial phase II drug-metabolizing enzyme, which glucuronidates various compounds, including clinical drugs and hormones. Mutants might affect glucuronidation, leading to a disruption of drug metabolism in vivo and decrease of therapeutic effect. Here, we mainly analyzed two representative mutants, H401P and L446S, on UGT2B15 activity using glucuronidation assays, molecular dynamic (MD) simulation and X-ray diffraction methods. The enzyme activity of L446S obviously increased six-fold than the wild type, although the enzyme activities of P191L, T374A, and H401P were lost apparently. Furthermore, we used MD simulations to calculate the energy change in the catalytic process of H401P and L446S, and the results indicated the free binding energies of H401P mutant to oxazepam and UDPGA were ?30.98 ± 1.00 kcal/mol and ?36.42 ± 1.04 kcal/mol, respectively, increased obviously compared to wild type, suggesting the mutation on position 401 had a crucial effect on the catalysis. Moreover, the three-dimensional structure of UGT2B15 C-terminal domain L446S was determined through protein crystallography and X-ray diffraction technology and the results suggested that one more hydrogen bonding between S446 and K410 was formed in the S446 crystal structure, compared to the wild type. Isothermal titration calorimetry assay further revealed the K_d values of C-terminal domain of UGT2B15 harbored L446S towards the cofactor UDPGA was similar to the value of wild type. Above all, our results pointed out that H401P and L446S affected the enzyme activity by different mechanism. Our work provided a helpful mechanism for variance explained in the UGTs catalyzation process.