A plasma/serum estrogen-binding protein distinct from testosterone-estradiol-binding globulin.

A plasma/serum estrogen-binding protein (E2BP) which is distinct from testosterone-estradiol-binding globulin (TEBG) has been documented. This high affinity, low capacity estrogen binder is readily detectable in the mannoglycoprotein fraction of serum or plasma. It can be distinguished from TEBG by 1) its isoelectric elution pH (pH 3.9 as distinct from pH 4.9 for TEBG); 2) its sedimentation value on sucrose gradients (a lower sedimentation value compared to TEBG); and 3) its steroid specificity (a high affinity for diethylstilbestrol with essentially no affinity for dihydrotestosterone or testosterone, in contrast to TEBG which has no affinity for diethylstilbestrol and a high affinity for dihydrotestosterone and testosterone).