The molecular weights of plasma and intestinal kallikreins in rats.

1. The molecular weights of kallikreins of rat intestine and rat plasma have been estimated using gel filtration. 2. Extracts of pooled tissue from rat jejunum, ileum, caecum and colon activated by autolytic processes gave a single peak of kallikrein activity with a molecular weights of 33000. 3. Acid-activated rat plasma gave two peaks of kallikrein activity with molecular weight of 125000 and 61500. 4. Rat intestinal tissue contains a kinin forming enzyme having a molecular weight similar to those of glandular kallikreins and different from those of the rat plasma kallikreins.