6865
We thus illustrate that G proteins and Zn ( 2 + ) act as two " keys " that control enzymatic activity of calnuc , arresting it in " locked " state .
 Zn ( 2 + )
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 Zn ( 2 + )