3664
Activity assays showed the UGT2A2 Delta exon3 protein ( termed UGT2A2 _ i2 ) exhibited no detectable glucuronidation activity against all substrates examined ; however , coexpression studies suggested that UGT2A2 _ i2 negatively modulates UGT2A2 _ i1 activity .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
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