1573
The active site histidine ( His - 438 ) was hypothesized to abstract o - hydroxybenzyl moiety from the initial adduct on Ser - 198 .
 Chemical: histidine; Chemical: His; Chemical: o - hydroxybenzyl; Chemical: Ser
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: His; Chemical: o - hydroxybenzyl; Chemical: Ser