21571
This activity requires a divalent metal cofactor Mn ( 2 + ) and is stimulated by 5 ' - phosphate ends of duplex DNA .
 Mn ( 2 + ), 5 ' - phosphate
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 Mn ( 2 + ), 5 ' - phosphate