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

Substrate	Human β-glucuronidase		E. coli β-glucuronidase
Substrate	pH 5.5	pH 7.0	pH 5.5	pH 7.0
	pmol product
BenzidineN-glucuronide	ND	0	ND	1 ± 1
N-AcetylbenzidineN-glucuronide	ND	0	ND	0
N′-Hydroxy-N-AcetylbenzidineN-glucuronide	ND	97 ± 4	ND	12
N′-Hydroxy-N-AcetylbenzidineO-glucuronide	73	115	154	91 ± 1
N′-Hydroxy-N,N′-DiacetylbenzidineO-glucuronide	100 ± 1	174 ± 16	253 ± 5	212 ± 10
3-Hydroxy-BenzidineO-glucuronide	148	222	100	0
3-Hydroxy-N,N′-DiacetylbenzidineO-glucuronide	195 ± 5	243 ± 6	72	30 ± 8
4-AminobiphenylN-glucuronide	ND	0	ND	5 ± 5
N-Hydroxy-4-AminobiphenylN-glucuronide	ND	180 ± 29	ND	0
N-Hydroxy-N-Acetyl-4-AminobiphenylO-glucuronide	97	174	294 ± 1	226

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.