19781
This potency improvement can be rationalized by X - ray crystallography , which shows a water - mediated contact between the basic nitrogen and the carboxylic acid side chain of Asp200 , which is situated at the mouth of the active site pocket of arginase II ( Asp181 in arginase I ) .
 Chemical: nitrogen; Chemical: carboxylic acid; Chemical: Asp200; Chemical: Asp181
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: nitrogen; Chemical: carboxylic acid; Chemical: Asp200; Chemical: Asp181