This rennin substrate is purified 390-fold from the serum by chromatography on Blue Sepharose, phenyl sepharose, hydroxyapatite and finally by affinity chromatography on 5-hydroxytryptamine (5-HT) sepharose to which it specifically binds to the 5-HT. It is applied to the latter column in 50mM sodium phosphate at pH 7 and after washing, it is eluted by increasing the ionic strength with 100mM sodium phosphate buffer containing 250mM NaCl. The multiple forms are separated by SDSPAGE and have pI 4.40-4.82. [Campbell et al. Biochem J 243 121 1987.]
