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The plant growth regulator ethephon ( 2 - chloroethylphosphonic acid ) inhibits human butyrylcholinesterase ( BChE ) by making a covalent adduct on the active site serine 198 .
 Chemical: ethephon; Chemical: 2 - chloroethylphosphonic acid; Chemical: serine
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: ethephon; Chemical: 2 - chloroethylphosphonic acid; Chemical: serine