Table 1

Human and E. coli β-glucuronidase hydrolysis of glucuronide conjugates of benzidine and 4-aminobiphenyl and their hydroxy metabolites at pH 5.5 and 7.0

SubstrateHuman β-glucuronidaseE. coli β-glucuronidase
pH 5.5pH 7.0pH 5.5pH 7.0
pmol product
BenzidineN-glucuronideND0ND1  ± 1
N-AcetylbenzidineN-glucuronideND0ND0
N′-Hydroxy-N-AcetylbenzidineN-glucuronideND97  ± 4ND12
N′-Hydroxy-N-AcetylbenzidineO-glucuronide7311515491  ± 1
N′-Hydroxy-N,N′-DiacetylbenzidineO-glucuronide100  ± 1174  ± 16253  ± 5212  ± 10
3-Hydroxy-BenzidineO-glucuronide1482221000
3-Hydroxy-N,N′-DiacetylbenzidineO-glucuronide195  ± 5243  ± 67230  ± 8
4-AminobiphenylN-glucuronideND0ND5  ± 5
N-Hydroxy-4-AminobiphenylN-glucuronideND180  ± 29ND0
N-Hydroxy-N-Acetyl-4-AminobiphenylO-glucuronide97174294  ± 1226

Glucuronides (6–12 μM) were incubated in 0.025 ml at 37°C for 30 min. Human β-glucuronidase was used at 822 and 5,480 U at pH 5.5 and 7.0, respectively. E. coli β-glucuronidase was used at 85 and 21 U at pH 5.5 and 7.0, respectively. Values represent the average of duplicate determinations from a single experiment or the mean ± S.E.M. of two or more experiments.

  • ND, not determined.