Wikipedia Article About Rennet on Wikipedia
Rennet is a substance used to coagulate milk, causing it to separate into solids (curds) and liquid (whey). The active enzyme in rennet is called rennin or chymosin (EC 18.104.22.168). The chief use of rennet is in the making of cheese and junket. The enzyme reacts with κ-casein on the surface of the casein micelle particles in the milk. This in the presence of calcium ions causes the coagulation of the casein micelles to form a curd. Commercially, rennet is sold in liquid, powder, and tablet forms.
Rennin reacts specifically with κ-casein, cleaving the protein between the amino acids phenylalanine(105) and methionine (106), producing two fragments. The soluble fragment (residules 106-169) which becomes part of the whey is known as glyco macro peptide and contains the glycosylation sites for κ-casein. The other component (residules 1-105) is insoluble.