This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
All of the following are trypsin inhibitors, except: 
Select and explain. 
A. Alpha - 1 antitrypsin, B. Alpha - 1 - antiproteinase, C. Enterokinase, D. Egg - white
C: Enterokinase
Answer: C: Enterokinase 
Explanation: Enterokinase is a glycoprotein enzyme that activates trypsin and is present in the brush border of intestine. Ref: Biochemistry By Mary K. Campbell, Shawn O. Farrell, 7th Edition, Page 176; Harper's Textbook of Biochemistry, 27th Edition, Page 597