Nuclear epoxide hydrolase in the human fetal and adult liver.

The epoxide hydrolase activity with styrene oxide as substrate was investigated in the nuclear fraction of human fetal and adult liver specimens. All investigated liver fractions catalyzed the hydration of styrene oxide and the average epoxide hydrolase activities were 0.37 and 1.90 nmol/min/mg protein in fetal and adult specimens, respectively. The enzyme followed Michaelis-Menten kinetics in fetal nuclear fraction and biphasic kinetics in adult livers. The nuclear/microsomal enzyme activity ratios of epoxide hydrolase were 0.09 and 0.11 for fetal and adult livers, respectively.