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. 1999 Mar 16;96(6):3149–3153. doi: 10.1073/pnas.96.6.3149

Figure 2.

Figure 2

Confirmation of IGF-dependent IGFBP-4 protease as PAPP-A. (a) Inhibition of IGFBP-4 protease activity in HFCM by PAPP-A/proMBP antibodies. HFCM was assayed for IGFBP-4 protease activity, as described in Fig. 1 and in Materials and Methods, in the presence of indicated titer of either PAPP-A/proMBP polyclonal antibody (anti-PAPP-A) or nonspecific rabbit IgG. (b) Immunodepletion of IGFBP-4 protease activity from HFCM by PAPP-A antibodies. HFCM was precleared with a 1:50 titer of nonspecific rabbit IgG. The precleared fractions were immunodepleted with indicated titer of PAPP-A/proMBP polyclonal antibody and assayed for IGFBP-4 protease activity. (c) IGF-dependent IGFBP-4 protease activity of purified PAPP-A. PAPP-A/proMBP (0.5 μg) purified from pregnancy sera was assayed for IGFBP-4 protease activity in the absence (-) and presence (+) of 5 nM IGF-II.