Efficient Removal of Cathepsin L from Active Cathepsin X using Immunoprecipitation Technique

Urša Pečar Fonović1,* and Janko Kos1,2

1 Faculty of Pharmacy, University of Ljubljana, A{kerčeva 7, 1000 Ljubljana, Slovenia
2 Department of Biotechnology, Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
* Corresponding author: ursa.pecarfonovic@ffa.uni-lj.si;
Tel.: +386 1 4769 500; Fax: +386 1 4258 031

Cathepsin X is a cysteine protease which is involved in various important physiological and pathological processes. For the purpose of biochemical and structural studies, pure and active cathepsin X is required without contamination with other related proteases. Recombinant cathepsin X was obtained by expression in methylotropic yeast Pichia pastoris. During purification, cathepsin X has to be activated with cysteine protease cathepsin L, however, separation methods, used so far, can not completely remove cathepsin L from the activated cathepsin X. Here we describe a new purification procedure which provides active recombinant cathepsin X without the presence of residual cathepsin L.

Keywords: Cathepsin X, cathepsin L, purification, immunoprecipitation