A kininogen-like substance in unheated human plasma proteins.

Abstract

The presence of a kininogen‐like substance was evidenced in unheated human plasma proteins. This substance was found to be susceptible to human urinary kallikrein and its content per gram dry weight of unheated plasma proteins was estimated to be equal to the amount of standard human kininogen that produces kinin activity equivalent to 2–8 μg bradykinin under the action of human urinary kallikrein.The elimination of this substance from unheated plasma proteins was achieved by chromatography on DEAE‐Sephadex equilibrated with pH 7.5 Tris buffer. The bradykinin‐like substance contained in 5 per cent heat‐treated human plasma protein solution was demonstrated to be released either by the heat treatment of unheated plasma protein solution at 60 C or by the enzymatic action of human urinary kallikrein. It is presumed that this kininogen‐like substance in unheated plasma proteins will be a precursor for the bradykinin‐like substance in 5 per cent heat‐treated human plasma protein solution.