20720
Here , we show that Whi3 is phosphorylated by the Ras / cAMP - dependent protein kinase ( PKA ) and that phosphorylation of Ser - 568 in Whi3 by PKA plays an inhibitory role in Whi3 function .
 Chemical: cAMP; 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: cAMP; Chemical: Ser