A rennin-sensitive bond in αs1Β-casein

Summary Rennin acts on a specially sensitive bond in αs1B-casein to produce a basic peptide containing residues 1–23 of the original protein. At pH 6·4 and 30°C, the action is specific and rapid, the kinetic constants beingKm4·5×10−4M,Kcat3·8 s−1, andkcat/Km0·85×104s−1M−1. Pepsin, and a protease impurity in the acid phosphatase from wheat germ, have a similar action.