Uridine diphosphate glucuronyl

In mice, intermediate-duration inhalation exposures at a concentration of 482 ppm for up to 23 days (4 hours a day, 5 days a week) have resulted in a marked reduction in cytochrome P-450 and cytochrome c-reductase content after 2-3 days. The level returned to normal by the 23 rd day of treatment. A significant decrease in uridine diphosphate-glucuronyl (UDP-glucuronyl) transferase was also noted, as well as a significant increase in lipid peroxidation (Jarvisalo et al. 1977a). Rabbits exposed to 300 ppm for 30 minutes a day for 120 days failed to develop any histopathologic alterations of the liver (Tsuyoshi 1959). However, because of the small sample size (n=3), the conclusions are preliminary. 

The enzyme and coenzyme for the above conjugation reactions are uridine diphosphate glucuronyl transferase and uridine-5 -diphospho-a-D-glucuronic acid, respectively.)... 

Studies of Felsher and Craig suggest an interference with the activity of the uridine diphosphate-glucuronyl transferase, eliminate the participation of jS-glucuroni-dase, but do not exclude the contribution of other unknown factors in the pathogenesis of Gilbert s disease [50]. 

This is the most common single metabolic reaction undergone by drugs, which occurs in the liver. These reactions are catalyzed by a family of enzymes known as uridine diphosphate (UDP) glucuronyl transferases. These enzymes are present in liver, kidney, intestine and lungs. 

It has now been established that in common with many other glu-curonides, bilirubin glucuronide can be synthesized in the adult rat, rabbit, mouse, and guinea pig liver by the enzymatic transfer of glucuronic acid from uridine diphosphate glucuronic acid to an acceptor substance, namely, bilirubin (Fig. 3) (B17, G5, L3, L5, S8). The transferring enzyme (glucuronyl transferase) has been shown by Schmid et al. 

Hollmann, S., and Touster, O., 1962, Alterations in tissue levels of uridine diphosphate glucose dehydrogenase, uridine diphosphate glucuronic acid pyrophosphatase and glucuronyl transferase induced by substances influencing the production of ascorbic acid, Biochim. Biophys. Acta 26 338-352. 

O-glucuronidation is catalysed by glucuronyl transferase that transfers a glucuronic acid moiety from uridine diphosphate glucuronide to an alcohol, phenol or carboxylic acid group (Fig. 8.36). This is the most important... 

Figure 8.36 Glucuronidation of a hydroxylated compound by UDP-glucuronyl transferase with uridine diphosphate glucuronide (UDPG) as the co-factor.

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