Kinin-forming enzyme (kininogenin) in homogenates of rat kidney

Abstract

An enzyme has been found in rat-kidney homogenates with the ability to release bradykinin or related peptides from plasma globulin. The system is normally inactive but can easily be activated in hypotonic media at pH 5.0.

Centrifugation studies have shown that most of the enzymatic activity is concentrated in particles with the sedimentation characteristics of lysosomes or droplets.

The sediment is inactive and can be activated by procedures used to release phosphate from lysosomes.

The kidney enzyme has many properties of the urinary kallikrein found in rat urine.