Definition of "protease"

As a matter of fact the casein protease digests boiled and coagulated serum far more easily than unboiled serum, as set forth by the following experiments.

1903 November 2, S. G. Hedin, “On the presence of a proteolytic enzyme in the normal serum of the ox”, in The Journal of Physiology, volume 30, number 2, page 195

All were tested for their ability to clot milk and to hydrolyze denatured hemoglobin, egg albumin, protamine (salmon), histone (calf thymus), and benzoyl-l-arginineamide. In no case was any trace of protease activity detected.

1948 September 20, Margaret R. McDonald, “A method for the preparation of "protease-free" crystalline ribonuclease”, in Journal of General Physiology, volume 32, number 1, page 39