Co-expression of human ABCG5 and ABCG8 in insect cells generates an androstan stimulated membrane ATPase activity.

Mutations in the ATP-binding cassette (ABC) proteins ABCG5 or ABCG8 cause sitosterolemia, a condition with increased accumulation of plant sterols. Upon high level expression of the ABCG5 and ABCG8 proteins in baculovirus-Sf9 cell expression system we found a distinct, vanadate sensitive ATPase activity in isolated membrane preparations only when the two proteins were co-expressed. This ATPase activity was significantly stimulated by the addition of certain androgen hormones and analogs, and was effectively inhibited by progesterone. Our results provide a new aspect of biochemical and functional characterization of the ABCG5/ABCG8 proteins and their possible involvement in steroid hormone transport or regulation.

[Laboratory studies of the antioxidant effect and free radical elimination of CoD tea]. / A CoD tea antioxidáns és gyökelimináló hatásainak laboratóriumi vizsgálata.

Free radical elimination properties of anticarcinogenic CoD tea were studied in vitro in our laboratory. Therefore its antioxidant effect, lipid-hydroperoxide elimination property and reductive capacity were measured. The isoenzyme composition of CoD tea lipoxygenases was deduced from pH dependence of its lipoxygenase activity. It was found that the antioxidant effect and lipid-hydroperoxide elimination property of CoD tea were comparable with those of ascorbic acid and the reductive capacity of a cup of CoD tea and 11-13 mg ascorbic acid were the same. In spite of the heat sensibility of lipoxygenases, a strong lipoxygenase activity (1102 U/g) of CoD tea was detected in acidic medium (pH 4.5). It is supposed that these free radical elimination properties support anticarcinogenic effect of CoD tea.