Study of a proteolytic enzyme from rabbit spleen

Abstract

The proteolytic activity of rabbit-spleen extracts towards human-serum albumin has been studied. With serum albumin as substrate a method of measuring the proteolytic activity of spleen extracts has been developed, based on the determination with the biuret reagent of the amount of products which are not precipitable by trichloroacetic acid. The enzyme responsible for this proteolytic activity has been purified by adsorption of inactive material on diethylaminoethylcellulose and carboxymethylcellulose. Chromatography on diethylaminoethylcellulose has demonstrated the existence of only one enzyme in the purified preparation. The optimum pH and the Michaelis constant of this enzyme are the same as those of the proteolytic activity in the crude preparation. It was therefore concluded that this enzyme is responsible for the proteolytic activity of the crude spleen extracts. A comparative study of the immunoelectrophoresis patterns give by human-serum albumin, degraded with the crude and purified spleen extracts, has shown that it is this enzyme which is responsible in both cases for the splitting of the antigenic structure of human-serum albumin.