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The composition of heterotrimeric PP2A holoenzymes , resulting from the combinatorial assembly of a catalytic C subunit , a structural A subunit , and regulatory B - type subunit , provides the essential determinants for substrate specificity , subcellular targeting , and fine - tuning of phosphatase activity , largely explaining why PP2A is functionally involved in so many diverse physiological processes , sometimes in seemingly opposing ways .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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