15868
A histidine - containing cavitein has been found to catalyze ester hydrolysis with a rate increase of 18 times that of background .
 Chemical: histidine; Chemical: ester
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: histidine; Chemical: ester