Abstract
An arginyl esterase, identified by hydrolysis of tosyl- l-arginine- O-methyl ester (TAME), is present in estrogen-stimulated, immature rat uterine cytosol. The esterase is Ca 2+-dependent and appears 3−8 h after injection of 4.5 μg of 17β-estradiol (E 2). The Ca 2+-independent TAME hydrolase activity in stimulated uteri decreases as the Ca 2+-dependent hydrolase activity increases. The TAME hydrolase activity is not increased by dexamethasone or testosterone, nor is it elevated in liver cytosol of the same E 2-treated rats. Rat plasma contains a potent Ca 2+-dependent TAME hydrolase activity distinguished from the uterine enzyme by its response to high Ca 2+ concentrations and its interaction with goat anti-rat serum inununoglobulin G. The uterine TAME hydrolase is apparently a trypsin-like serine protease, as defined by its pattern of inhibition, e.g. response to diisopropylfluorophosphate. The Ca 2+-dependent hydrolase kinetics are complex, with an initial lag phase followed by a dramatic acceleration in the rate of hydrolysis. Both the length of the lag phase and the extent of acceleration vary with the amount of cytosol. The metal requirement is specific for Ca 2+. The endogenous substrate of this newly recognized, estrogenstimulated TAME hydrolase and its role in uterine development remain to be elucidated.
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