19511
Two of the 5 natural cysteines , Cys27 and Cys219 , are essential for enzymatic activity and form a disulfide bridge .
 Chemical: cysteines; Chemical: disulfide
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: cysteines, disulfide 
Answer:
 Chemical: cysteines; Chemical: disulfide