Κ-casein, or kappa casein, is a mammalian milk protein involved in several important physiological processes.  Chymosin (found in rennet) splits K-casein into an insoluble peptide (para kappa-casein) and  water-soluble glycomacropeptide (GMP). GMP is responsible for an increased efficiency of digestion, prevention of neonate hypersensitivity to ingested proteins, and inhibition of gastric pathogens. The human gene for κ-casein is CSN3.