Rennin.--In the stomach, the digestion of proteins is due to the action of pepsin, the coagulation of the casein of milk to the action of rennin. According to some authorities, pepsin and rennin are two distinct enzymes. According to other authorities, the two reactions (proteolysis and coagulation) are produced catalytically by two different side chains of the same molecule. Pepsin in the crystalline state has been known for several years. ISRAEL S. KLEINER (Hahnemannian 3lonthly, 1933, LXVIII, 61o-613) endeavored to crystallize rennin obtained from the fourth stomach of the calf. While he failed to obtain crystals, his final, concentrated product had an activity of I : 4,500,000, i.e., one part of the rennin produced coagulation of 4,500,000 parts by weight of skimmed milk. This rennin possessed practically no power to digest egg albumin in acid solution, therefore differed from pepsin. The two enzyme preparations (crystalline pepsin and concentrated rennin) differed in other respects, e.g., in behavior on dialysis, reactions for precipitation, and response to color tests. Pepsin and rennin are separate and distinct enzymes. Rennin apparently is a thioproteose, pepsin a simple protein.
J. s. H.