UDP-glucosyltransferase

The enzyme UDP-glucosyltransferase is involved in the detoxication of xeno-biotics. Whereas vertebrates carry out glucuronidation by using UDP-glucuronic acid, invertebrates and plants form the glucoside derivatives with UDP-glucose as the donor of the glucosyl moiety. 

Separation of 4-nitrophenol and 4-nitrophenol glucoside was obtained on a Tracer Spherisorb ODS-2 column (4.6 mm x 250 mm, 5 /Am). The mobile phase was 10 mM potassium phosphate buffer (pH 7.1) in 15% methanol. The absorbance at 295 nm was used for quantitation. 

The standard reaction mixture contained in a Anal volume of 0.25 mL 16 mM MgCl2, 6.4 mM UDP-glucose, 3.2 mM p-nitrophenol, enzyme extract (100-500 /tg of protein) and 0.1 M Tris-HCl buffer (pH 8.0). After a 20-minute incubation at 43°C, the reaction was terminated by the addition of 20 /aL of 40% perchloric acid. The supernate obtained by centrifugation was Altered and then subjected to HPLC analysis. Formation of product was linear with time up to 40 minutes and with protein added in the range of 0 to 5.5 mg protein/mL. Alternative substrates for the enzyme include 1-naphthol and 2-naphthol. 

The enzyme source was derived from homogenates of Drosophila melano-gaster. 

---

McIntosh C, Mansell R (1990) Biosynthesis of naringin in Citrus paradisi UDP-glucosyltransferase activity in grapefruit seedlings. Phytochemistry 29 1533-1538... 

System is also applied to assay bilirubin UDP-xylosyl- and/or bilirubin UDP-glucosyltransferase activity. 

Figure 3.7 Biosynthesis of cyanogenic glucosides. The biosynthetic pathway of cyanogenic glucosides exemplarily is mentioned for dhurrin. The biosynthesis is performed by the two multi-functional cytochrome P450 enzymes and a UDP-glucosyltransferase. All three enzymes are joined together in a metabolon located in the ER-membrane (according to Nielsen et al., 2008).

Due to the electrophilic nature of the molecules it is not surprising that DIBOA and DIMBOA were found to inactivate a number of enzymes unspecifically, such as aphid cholinesterase, UDP-glucosyltransferase, plasma membrane ATPase, chymotrypsin, papain, and ribonucleotide reductase [3]. One can speculate that a large number of cellular pathways, e.g., the ubiquitin-proteasome dependent selective protein degradation, where SH-groups of E-enzymes and lysine residues of target proteins are of crucial importance, may be affected [138]. 

A patient in a nursing home who developed severe diarrhea was diagnosed with a Clostridium dijficile infection. The severe diarrhea associated with C. dijficile is caused principally by two toxins that are UDP-glucosyltransferases. These toxins modify a monomeric G protein, thereby disrupting cellular attachments associated with the actin skeleton. 

Timmers CM, Dekker M, Buijsman RC, van der Marel GA, Ethell B, Anderson G, Burchell B, Mulder GJ, van Boom JH (1997) Synthesis and inhibitory effect of a trisubstrate transition state analog for the UDP glucosyltransferases. Bioorg Med Chem Lett 7 1501-1506... 

In the latter species, UDP-glucosyltransferase activity was mainly present in intestinal tissues, with activity also in the digestive gland but not in the skin or muscle tissue (Dutton 1966). The intestinal activity of A. ater (substrate o-aminophenol) was mainly microsomal, had a pH optimum of 9.3 and was stimulated by magnesium ions (Dutton 1966). Glucosyltransferase activities have been indicated in P. acuta (towards phenols liberated from fenitrothion) and C. stelleri (towards / -nitrophenol) (see Sect. 7.2.2). 

Leakey JEA, Dutton GJ (1975) Effect of phenobarbital on UDP-glucosyltransferase activity and phenolic glucosidation in the mollusc Arion ater. Comp Biochem Physiol 51C 215-217 LeBlanc GA, Cochrane BJ (1987) Identification of multiple glutathione S -transferases from Daphnia magna. Comp Biochem Physiol 88B 39-45... 

Mulichak, A.M. et al. (2001) Structure of the UDP-glucosyltransferase GtfB that modifies the heptapeptide aglycone in the biosynthesis of vancomycin group antibiotics. Structure 9, 547-557... 

Poppenberger, B. et al. (2003) Detoxification of the Fusarium mycotoxin deoxynivalenol by a UDP-glucosyltransferase from Arabidopsis thaliana. J. Biol. Chem. 278,47905 7914... 

Sepulveda-Jimenez, G. et al. (2005) A red beet Beta vulgaris) UDP-glucosyltransferase gene induced by wounding, bacterial infiltration and oxidative stress. J. Exp. Bot. 56, 605-611... 

A novel approach to increase the insecticidal properties of NPV was demonstrated by O Reilly and Miller (30). The researchers deleted an indigenous gene that encodes for ecdysteroid UDP-glucosyltransferase (EOT) from the AcNPV genome. EOT transfers the sugar moiety from a UDP-sugar to ecdysone, effectively... 

---