Acid Protease of Bovine Milk

Abstract

Occurrence of milk acid protease in bovine casein in addition to alkaline protease was found and purification of this enzyme was achieved. The enzyme had a pH optimum at 4.0 and was most stable at pH 3.5. The molecular weight of the enzyme was 36, 000 and no inhibition was observed by diisopropyl-fluorophosphate, EDTA etc. This enzyme is considered to be similar to cathepsin D.
Milk acid protease mainly hydrolyzed α_s-casein and similar change was observed in autolysis of casein at pH 5.5. It is suggested that milk acid protease may have some significance in cheese ripening.