Purification of the gonadotropin-releasing hormone-degrading enzyme by affinity chromatography

A crude preparation of Kallikrein inactivator, which inhibits the gonadotropin-releasing hormone (GnRH)-degrading enzyme(s) from rat hypothalamus and anterior pituitary, was fractionated by passage through an ion-exchange column. The enzyme-inhibiting fraction was coupled to Sepharose and the resin obtained was used for, affinity-chromatography purification of the GnRH-degrading enzyme. The enzyme from crude tissue preparations was retained on this column and eluted by 0.05 M phosphate buffer. A 9-12 fold increase in the specific activity of the enzyme was achieved. Bacitracin, an effective peptide inhibitor of the degradation of GnRH, was also coupled to Sepharose. Three different such Sepharose-bacitracin conjugates were synthesized, two of which inhibited the degradation of GnRH by hypothalamic and pituitary extracts. They all failed, however, to separate the active enzymic fraction from the bulk of accompanying proteins, using affinity chromatographic techniques.