Electrophoretic analysis of membrane proteases in the luteinized rat ovary

Membrane fractions from fully luteinized rat ovaries contained proteolytic enzymes that were solubilized and reversibly inhibited by the anionic detergent sodium dodecyl sulfate. Electrophoretic analysis in substrate-containing sodium dodecyl sulfate-polyacrylamide slab gels revealed the presence of numerous protease bands in the mol wt range of 26,000 to more than 200,000. When casein served as protease substrate in the gels, enzyme bands of Mr 26,000, 28,000, 30,000, and 90,000 were produced by crude (2,000 X g pellet) ovarian membranes. Gels containing casein and plasminogen also revealed the presence of two plasminogen activators of Mr 63,000-65,000 and 42,000. Subcellular fractionation of luteinized ovaries by centrifugation in sucrose density gradients indicated that the Mr 90,000 protease and the two plasminogen activators were uniformly distributed among microvillous membranes, basolateral membranes (BLM), and the mitochondrial-lysosomal fraction (MLF). The Mr 26,000, 28,000, and 30,000 proteases were enriched in BLM and MLF. Analysis of crude membranes in slab gels which contained gelatin as the protease substrate revealed the presence of two additional enzymes of Mr 52,000 and more than 200,000. The Mr greater than 200,000 protease was present in microvillous membranes, BLM, and MLF. The Mr 52,000 protease was found exclusively in BLM. This enzyme was not consistently demonstrable in crude membranes but could be generated upon incubation of membranes at 30 C. This finding indicated that Mr 52,000 protease can exist in an inactive and/or zymogen form. The Mr 90,000 protease was inhibited by tosyl-lysine chloromethyl ketone and dansyl-glutamyl-glycylarginine chloromethyl ketone. The gelatinase activity of the Mr 52,000 protease was blocked by tosyl lysine chloromethyl ketone, dansyl-glutamyl-glycylarginine chloromethyl ketone and tosylamide-2-phenyl chloromethyl ketone. The activity of the Mr 26,000, 28,000, and 30,000 proteases was not affected by any of the above mentioned inhibitors. These findings demonstrate that the proteolytic potential of ovarian membranes is not limited to plasminogen activators. Numerous plasminogen-independent proteases are also present, and these may play a role in ovulation, luteolysis, and mediation of hormonal stimulation.