Why do we have an enzyme activity that seems harmful?
The liver has conjugated some toxin with glururonic acid for elimination by the kidneys or the intestines via bile, and glucuronidase de-conjugates it before it gets into the blood stream.
Hypothesis: glucuronidase is an enzyme involved in toxic load balancing, a system with many parts. In the first part, the liver puts some fat soluble toxins directly into bile and the intestines feel this toxicity most acutely. In the other part, the liver renders toxins sufficiently water-soluble that the rest of the body experiences them and the kidneys have to filter them, and then “fail” to re-absorb the toxin, releasing it into the urinary bladder, which most acutely feels the toxins presence until voiding. Some excess vitamin C to keep the bladder happy, anyone? Anyone feel like more frequent and more complete voiding of the bladder might be a good idea?
Hypothesis: another part to the toxic load balancing system. When the kidney (or urinary bladder) is overloaded, it/they signal/s the liver to shunt more toxins toward the intestines. These signals may decrease conjugases and/or increase glucuronidase and other de-conjugating enzymes. In this way, the digestive tract shares more of this toxic load. The digestive tract can probably do the same thing: it can signal the liver to shunt more toxins toward the kidneys and bladder. Competition and proper functioning ensures proper toxic load balancing.
For those whose bowels are healthier than their kidneys, activation of de-conjugating enzymes or reduction in activity of conjugating enzymes may make some temporary medical sense.