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Poly ( ADP - ribose ) polymerases ( PARPs ) or diphtheria toxin like ADP - ribosyl transferases ( ARTDs ) are enzymes that catalyze the covalent modification of proteins by attachment of ADP - ribose units to the target amino acid residues or to the growing chain of ADP - ribose .
 Poly ( ADP - ribose ), ADP, ribosyl, ADP, ribose, amino acid, ADP, ribose
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 Poly ( ADP - ribose ), ADP, ribosyl, ADP, ribose, amino acid, ADP, ribose