Studies on β-Glucuronidase of the Developing Human Placenta

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Abstract
Subfractional activities and some properties of Β-glucuronidase were studied at different ontogenetic stages of the human placenta. Maximum activity was localized in the 105,000 g supernatant of tissue homogenate. The enzyme activity in all fractions increased gradually, being maximum in the placentas of 22–26 weeks of gestation. At term, Β-glucuronidase activity had diminished to a great extent. The enzyme showed considerable stability after heating at 65 °C for 10 min. The Km value of this enzyme for p-nitrophenyl-Β-.D-glucuronide was 1.02 mM. EDTA inhibited placental Β-glucuronidase. Of the cations tested, Ag+, Fe++ and Co++ were stimulatory, while Zn++ was inhibitory to the enzyme. Only one isoenzyme of (Β-glucuronidase was found in human placenta.