ASSOCIATION OF SOME HYDROLYTIC ENZYMES WITH THE PROSTASOME MEMBRANE AND THEIR DIFFERENTIAL RESPONSES TO DETERGENT AND PIPLC TREATMENT

Prostasomes are human prostate derived organelles that were isolated f rom both prostatic fluid and seminal plasma for the present study. Spe cific activities were determined for prostasome membrane-associated en zymes, alkaline phosphatase (ALP), 5'-nucleotidase (5'NT), and alkalin e phosphodiesterase I (APD). The mode of their membranous anchoring wa s studied by treatment of prostasomes with phosphoinositol-specific ph ospholipase C (PIPLC) and different detergents. A substantial amount o f ALP (50%) and 5'NT (31%) was released by incubation of prostasomes w ith 2 U/ml of PIPLC contrary to the small amount of APD (12%) released by the same treatment. After PIPLC treatment, the enzymes were recove red in the aqueous phase after phase repartition in Triton X-114 indic ating that PIPLC removed the hydrophobic domain converting the enzymes from membrane-linked to aqueous soluble forms. Octyl glycoside was th e most efficient one among different detergents to solubilize the enzy mes from the prostasome membrane. Both ALP and 5'NT were resistant to the treatment with Triton X-100 and Triton X-114. These results sugges t that ALP, 5'NT, and APD are more or less extensively linked to the p rostasome membrane via a glycophosphoinositide anchor. (C) 1995 Wiley- Liss, Inc.