The kinds and activities of proteolytic enzymes in the digestive systems (tongue, esophagus, stomach, duodenum, liver, pancreas and large intestine) of two Amur tiger cubs (Panthera tigris altaica) were investigated using protein detection and SDS-G-PAGE. The results showed:1) the digestive system of Amur tiger cubs had 30 different kinds of proteolytic enzymes ; 2) the mostly optimal pH for these enzymes was a neutral environment, and an acid condition highly restrained their activity; 3) the proteolytic enzymes in the tongue and esophagus were fewer than in other digestive organs and their activities were weak as well; 4) the duodenum had the most kinds of proteolytic enzymes with the strongest activities under various pH conditions; 5) the 16 kD enzyme bands always existed under neutral and alkalescence pH conditions in all digestive organs except the tongue.
