Human biliary beta-glucuronidase: correlation of its activity with deconjugation of bilirubin in the bile

Total and conjugated bilirubin contents of gall-bladder and hepatic biles before and after 24-h incubation at 37 degrees C and beta-glucuronidase activity of hepatic biles were determined in forty-eight patients divided equally into four groups: no stones or control (C), cholesterol stones (CS), black pigment stones (black PS), and brown pigment stones (brown PS). The percent conjugation of bilirubin is lower in gall-bladder biles and hepatic biles after incubation, particularly in black PS and brown PS, when compared with hepatic biles before incubation. Mean endogenous beta-glucuronidase activities at pH 5.2 were 12.0, 15.5, 44.5 and 147.7 nmol min-1 ml-1 for C, CS, black PS, and Brown PS, respectively, which correlated well with the degree of deconjugation of bilirubin in gall-bladder and hepatic biles and with the rate of deconjugation of hepatic bile incubated at 37 degrees C. Only four biles in brown PS exhibited bacterial enzyme activity. We concluded that though bacterial beta-glucuronidase might be responsible for deconjugation of bilirubin in some patients in brown PS, endogenous biliary beta-glucuronidase could play a key role in the pathogenesis of pigment cholelithiasis.