Chymosin, Pepsins, and Other Aspartyl Proteinases: Structures, Functions, Catalytic Mechanism and Milk-Clotting Properties

This chapter comprehensively reviews the classification, structure, function, catalytic mechanism and milk-clotting properties of chymosin, pepsin and other aspartyl proteinases. Microbial rennets, recombinant chymosin and plant coagulants are discussed in detail. Hydrolysis of the principal bovine milk proteins (β-, αs-, and κ-caseins) by calf chymosin is described, as is the hydrolysis of caseins from the milk of other, nonbovine, species. Rennets other than chymosin are discussed and their hydrolysis of caseins described. Interspecies milk coagulation is reviewed and includes detail on the chymosins of several nonbovine species, including, camel, piglet, equine, New World monkey, rat and seal. The milk-clotting ability of aspartyl proteinases from other sources, for example, plants, fish and crustaceans is discussed.