Studies on beta-glucuronidase of the developing human placenta.

Subfractional activities and some properties of Beta-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, Beta-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-Beta-D-glucuronide was 1.02 mM. EDTA inhibited placental Beta-glucuronidase. Of the cations tested, Ag+, Fe++ and Co++ were stimulatory, while Zn++ was inhibitory to the enzyme. Only one isoenzyme of Beta-glucuronidase was found in human placenta.