Proteolytic release of dehydrodolichyl diphosphate synthase from pig testis microsomes

Pig testicular dehydrodolichyl diphosphate synthase was released in a soluble form out of microsomes by controlled proteolysis with trypsin or papain. Approximately 25% of the microsomal enzyme activity was recovered in the 115,000 x g supernatant fraction when the microsomes were treated with trypsin at 4 degrees C for 1 h. Similar proteolytic release of microsomal enzyme was also observed with the treatment with papain. The K(m), optimal pH, Mg2+ dependency, and ion strength dependency of the enzyme released by trypsin were similar to those of the microsomal enzyme. The microsomal enzyme was active even in the absence of detergents, while the released enzyme required detergents for activity. Gel filtration of the released enzyme gave a peak of dehydrodolichyl diphosphate synthase activity, which appeared between 150-kDa and 50-kDa molecular mass markers.