Characterization and purification of pregnancy-associated plasma protein B (PAPP-B)

PAPP-B is a pregnancy-specific beta 1-glycoprotein of large molecular weight, about 1,000,000 as determined by Sepharose 4B and 6B gel filtration. Its isoelectric point is between pH 4.6 and 5.0. It has been purified at least 800-fold from term pregnancy serum by a sequence of steps involving salting out at 30% saturation with ammonium sulfate (1,2M), DEAE-cellulose chromatography, Sepharose 4B gel filtration and hydroxylapatite chromatography. Monospecific antiserum to PAPP-B has been prepared, and used to differentiate it from several other newly reported tumor or pregnancy proteins. PAPP-B was found to increase slowly during the second trimester of pregnancy and more steeply during the third, reaching a plateau in late gestation. During the postpartum period, PAPP-B disappeared quite rapidly, with an apparent half-life of less than 1 day.