Different biochemical properties of nuclear and microsomal estrone-3-sulfatases: evidence for the presence of a nuclear isozyme.

In female rats, total estrone-3-sulfatase activity per liver in the nuclear fraction is comparable to the total activity per liver in the microsomal fraction. The combined estrone-3-sulfatase activity in the other fractions (lysosomal, mitochondrial, and cytosolic fractions) is negligible and only accounts for < 5% of the total nuclear or microsomal sulfatase activity. Nuclear and microsomal estrone-3-sulfatases have different pH optima (pH 8.0 and 7.2, respectively). The apparent Km values for the nuclear and microsomal estrone-3-sulfatases are 2.5 and 10.1 microM, respectively, suggesting that the nuclear sulfatase has a considerably higher affinity for estrone-3-sulfate than the microsomal sulfatase. Moreover, the nuclear estrone-3-sulfatase is more sensitive to inhibition by several steroids than the microsomal sulfatase. The results suggest that estrone-3-sulfatase in the nuclear fraction is a different isozyme than that in the microsomal fraction.