Dissertation
UTILIZATION OF ALTERNATIVE UDP-SUGARS IN THE METABOLISM OF POLYCYCLIC AROMATIC HYDROCARBONS BY UDP-GLYCOSYLTRANSFERASES
Doctor of Philosophy (PhD), Washington State University
01/2020
Handle:
https://hdl.handle.net/2376/117485
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are potent environmental carcinogens and are a primary risk factor for tobacco-related cancers. The detoxification of PAHs by glucuronidation is well-characterized for the UDP-glycosyltransferase (UGT) 1A, 2A, and 2B subfamilies; however, the role of the UGT3A subfamily in PAH metabolism remains poorly understood. The 1A, 2A, and 2B subfamilies utilize UDP-glucuronic acid as a cosubstrate, while the UGT3A subfamily uses alternative cosubstrates (UDP-N-Acetylglucosamine for UGT3A1, UDP-glucose and UDP-xylose for UGT3A2). In a western blot analysis, UGT3A1 exhibited the highest expression in liver with the floor of mouth exhibiting the lowest expression. UGT3A2 exhibited the highest expression in the floor of mouth and the lowest expression in liver. Limited glycosylation activity against PAHs was observed for UGT3A1 while UGT3A2 exhibited activity against all the PAHs tested. Since UGT3A2 had higher affinity for most PAHs when compared to the UGTs that use UDP-glucuronic acid, the functional effects of UGT3A2 missense variants on PAH metabolism were examined. There was a significant (P<0.05) decrease in glycosylation activity (Vmax/Km) against PAHs using both co-substrates for the seven variants (Y74N, D140N, A344T, S435Y, R445C, A436T, R445C, and Y474C) when compared to wild-type UGT3A2. The kinetics of the UDP-sugars showed that there was a better affinity for wild-type UGT3A2 and variants for UDP-glucose when compared to UDP-xylose. The UGT3A2 variants exhibited up to a 16-fold higher Km than wild-type UGT3A2 for UDP-glucose, while there was only a 5.5-fold higher Km for UDP-xylose. Other UGTs were tested to determine if they also use alternative co-substrates to detoxify PAHs. UGT1A7, 1A9, 1A10, and 2A1 exhibited glycosylation activity against 1-OH-pyrene using both UDP-glucose and UDP-xylose. Additionally, UGT1A8 and 1A10 exhibited glycosylation activity against 3-OH-B(a)P using both UDP-glucose and UDP-xylose, whereas UGT1A1, 1A7, 1A9, and 2A1 were active against 3-OH-B(a)P only with UDP-xylose. Liver, kidney, and intestine exhibited glycosylation activity against 1-OH-B(a)P and 3-OH-B(a)P with UDP-glucuronic acid, UDP-glucose, and UDP-xylose as co-substrates. These data suggest that alternative co-substrates play an important role in detoxifying PAHs and that UGT3A2 missense variants decrease the detoxification of PAHs, potentially resulting in an altered risk for PAH-related cancers.
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Details
- Title
- UTILIZATION OF ALTERNATIVE UDP-SUGARS IN THE METABOLISM OF POLYCYCLIC AROMATIC HYDROCARBONS BY UDP-GLYCOSYLTRANSFERASES
- Creators
- Ana Gabriela Vergara
- Contributors
- Philip Lazarus (Advisor)Gang Chen (Committee Member)Salah-uddin Ahmed (Committee Member)John Clarke (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Pharmacy and Pharmaceutical Sciences, College of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 178
- Identifiers
- 99900581610801842
- Language
- English
- Resource Type
- Dissertation